A method and system for transient classification processing of nuclear power units

Abstract

This invention discloses a transient classification and processing method and system for nuclear power units. It performs initial classification of transients generated by nuclear power units, and conducts secondary discrimination for transients that cannot be classified into the corresponding category. For unclassified transients, it provides classification suggestions for design transients. If the alternating stress intensity of each key component is less than the corresponding material fatigue limit, the unclassified transient is classified as a suggested design transient. Otherwise, further judgment is needed for the key components that do not meet the conditions. If the fatigue service factor caused by the unclassified transient is less than the fatigue service factor caused by the suggested design transient, the unclassified transient is classified as a suggested design transient. The transient classification and processing method and system provided by this invention classifies unclassifiable operational transients by evaluating the fatigue damage to mechanical components caused by the transient, greatly improving the efficiency of current transient classification and counting.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant performance testing technology, and in particular to a transient classification and processing method and system for nuclear power units. Background Technology

[0002] During operation, nuclear power plants must ensure the integrity of the pressure boundary of the reactor main loop, requiring monitoring of changes in parameters such as pressure and temperature. These parameter changes are collectively referred to as transients. Nuclear power plants need to classify operational transients as design transients based on their causes and count the occurrence of these design transients. However, in actual operation, due to unforeseen reasons, parameters such as temperature and pressure in the main loop system may experience sub-loop fluctuations, making it impossible to classify these operational transients. Figure 1 As shown, each transient event in a nuclear power unit causes a certain amount of fatigue damage to its mechanical components. Unclassified transients indicate a deviation between the actual operating state and the design state of the unit, and there is a risk that the original fatigue design analysis data for the mechanical components may no longer be applicable.

[0003] The above background information is provided only to assist in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application, nor does it necessarily provide technical teaching. In the absence of clear evidence that the above information was disclosed before the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a transient classification processing method for nuclear power units, the specific technical solution of which is as follows:

[0005] On the one hand, a transient classification and processing method for nuclear power units is provided. When classifying transients generated by nuclear power units, if the transient cannot be classified due to the presence of sub-cycle fluctuations, the sub-cycle fluctuations should be ignored first, and then a classification suggestion should be given for the transient based on the unit operation log, transient monitoring data and transient design documents.

[0006] The classification recommendations are verified through the following steps: Calculate the alternating stress intensity corresponding to each stress cycle of each key component on the nuclear power unit under the transient action; if the alternating stress intensity corresponding to each key component under the sub-cycle fluctuation is less than the fatigue limit of the corresponding material, then the transient is classified as a recommended design transient; otherwise, calculate the fatigue service factor caused by the key components that do not meet the conditions under the transient and the recommended design transient, respectively; if the fatigue service factor caused by the transient is less than the fatigue service factor caused by the recommended design transient, then the transient is classified as a recommended design transient.

[0007] Furthermore, providing classification suggestions for the transients includes the following steps:

[0008] First, ignore the sub-cycle fluctuations in the transient, determine the cause of the transient based on the nuclear power unit operation log, and then find the corresponding design transient in the design transient list;

[0009] The monitoring data of the transient is compared with the limit value of the design transient. If the monitoring data meets the corresponding limit requirements, the design transient is used as the initial classification suggestion.

[0010] Furthermore, the process for obtaining the alternating stress intensity of the key component under the transient action is as follows:

[0011] The finite element method was used to establish mechanical analysis models for the corresponding key components;

[0012] According to the RCCM specification, the stress cycle pairing and corresponding alternating stress intensity of the corresponding key parts under the transient state are obtained by calculation.

[0013] Based on the time of occurrence of the transient neutron cycle fluctuation, the alternating stress intensity corresponding to the neutron cycle fluctuation can be further determined.

[0014] Furthermore, the corresponding fatigue limit is obtained from the fatigue life curve of the corresponding material in the key parts, and the alternating stress intensity corresponding to the sub-cycle fluctuation of each key part is compared with the fatigue limit of the corresponding material. If the alternating stress intensity corresponding to the sub-cycle fluctuation of each key part is less than the fatigue limit of the corresponding material, the transient is classified as the suggested design transient, and the number of occurrences of the design transient is increased by one.

[0015] Furthermore, the design transient limits include temperature limits, pressure limits, temperature change rate limits, and pressure change rate limits. The monitoring data of the transient must all correspond to limits less than or equal to the design transient limits in order to use the design transient as an initial classification suggestion.

[0016] Furthermore, the transient includes one or more sub-cycle fluctuations, and the fatigue use factor of the transient is equal to the sum of the fatigue use factors corresponding to all sub-cycle fluctuations plus the fatigue use factor corresponding to the main transient fluctuation.

[0017] Furthermore, if the alternating stress intensity corresponding to each sub-cycle fluctuation of the critical component is less than the fatigue limit of the corresponding material, then the transient is classified as a suggested design transient.

[0018] Furthermore, if there is a critical component that does not meet the conditions, the fatigue service factor caused by the transient is greater than the fatigue service factor caused by the recommended design transient, then the transient cannot be classified as the recommended design transient, and other transient classification methods must be used for processing.

[0019] Furthermore, if the transient cannot be classified into any category in the transient design file, then the transient is created as a new design transient category;

[0020] Based on the historical log data of the nuclear power unit, the design transients of the newly established category are defined and fatigue damage is analyzed to obtain the corresponding number of safe cycles and the transient limits used for judgment.

[0021] Furthermore, when the number of design transient statistics exceeds the number of design occurrences, it is necessary to update the number of design occurrences and demonstrate that the critical components will not experience fatigue fracture failure under the new number of design occurrences.

[0022] Furthermore, the key components include: the connection nozzle between the hot section of the main pipeline and the RRA system, the connection nozzle between the cold section of the main pipeline and the RCV system drain line, the reactor pressure vessel inlet nozzle, the reactor pressure vessel outlet nozzle, the geometric discontinuity area of ​​the main pump casing, the coolant inlet nozzle of the steam generator main loop, the steam generator lower head, the manhole bolts of the steam generator lower head, and the connection area between the steam generator lower head and the tube sheet.

[0023] On the other hand, a transient classification processing system for nuclear power units is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the transient classification processing method described above.

[0024] Compared with the prior art, the present invention has the following advantages: it avoids searching for the cause of transients, and classifies unclassifiable operational transients by evaluating the fatigue damage to mechanical components caused by transients, which greatly improves the efficiency of current transient classification and counting. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the curve of an unclassified transient containing sub-cyclic fluctuations in the transient classification processing method provided in this embodiment of the invention;

[0026] Figure 2 This is a flowchart illustrating the analysis and classification process of unclassified transients containing sub-cyclic fluctuations in the transient classification processing method provided in this embodiment of the invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0029] In one embodiment of the present invention, a transient classification processing method for nuclear power units is provided. When classifying transients generated by nuclear power units, if the transients cannot be classified due to the presence of sub-cycle fluctuations, the sub-cycle fluctuations should be ignored first, and then a classification suggestion should be given for the transients based on the unit operation log, transient monitoring data and transient design documents.

[0030] The classification recommendations are verified through the following steps: Calculate the alternating stress intensity corresponding to each stress cycle of each key component on the nuclear power unit under the transient action; if the alternating stress intensity corresponding to each key component under sub-cycle fluctuations is less than the fatigue limit of the corresponding material, then the transient is classified as a recommended design transient; otherwise, calculate the fatigue service factor caused by the unsatisfactory key components under both the transient and the recommended design transient. If the fatigue service factor caused by the transient is less than the fatigue service factor caused by the recommended design transient, then the transient is classified as a recommended design transient. If an unclassified transient is classified as a recommended design transient, the occurrence count of the corresponding recommended design transient is increased by one. When the number of design transient occurrences exceeds the design occurrence count, the design occurrence count needs to be updated, and it must be demonstrated that the key components will not experience fatigue fracture failure under the new design occurrence count.

[0031] In one embodiment of the present invention, providing a classification suggestion for the transient includes the following steps: first, ignoring the sub-cycle fluctuations in the transient, determining the cause of the transient based on the nuclear power unit's operation log, and then identifying the corresponding design transient in the design transient list; comparing the monitoring data of the transient with the limits of the design transient, and if the monitoring data meets the corresponding limit requirements, then the design transient is used as an initial classification suggestion. The limits of the design transient include temperature limits, pressure limits, temperature change rate limits, and pressure change rate limits. The monitoring data of the transient must all correspond to limits less than or equal to the limits of the design transient for the design transient to be used as an initial classification suggestion.

[0032] If the transient includes multiple sub-cycle fluctuations, the transient can only be classified as a recommended design transient if the alternating stress intensity corresponding to each sub-cycle fluctuation in the critical part is less than the fatigue limit of the corresponding material.

[0033] The calculation process for the alternating stress intensity of the key components under the transient action is as follows: A mechanical analysis model of the corresponding key components is established using the finite element method; according to the RCCM standard, the stress cycle pairing and corresponding alternating stress intensity of the corresponding key components under the transient action are calculated; based on the time of the sub-cycle fluctuation in the transient action, the alternating stress intensity corresponding to the sub-cycle fluctuation is further determined. Under one-dimensional stress conditions, the value of the alternating stress intensity is equal to half of the stress change range within the corresponding time period. For example, if the stress change range of a certain key component is 100 MPa within a 10-minute sub-cycle time, then the alternating stress intensity corresponding to this sub-cycle fluctuation is 50 MPa.

[0034] If the alternating stress intensity of key components under sub-cycle fluctuations is greater than or equal to the fatigue limit of the corresponding material, a fatigue service factor comparison and discrimination process is required. The fatigue service factors caused by the key components that do not meet the conditions are calculated under the stated transient and the suggested design transient, respectively. If the fatigue service factors caused by the stated transient are all less than the fatigue service factors caused by the suggested design transient, then the transient is classified as the suggested design transient.

[0035] The fatigue service factor reflects the amount of fatigue damage caused by a single transient event and is numerically equal to the reciprocal of the allowable number of cycles. The proposed design transient does not contain sub-cycle fluctuations; the fatigue service factor of this design transient is equal to the fatigue service factor corresponding to its main fluctuation. If the transient includes one or more sub-cycle fluctuations, the fatigue service factor of the transient is equal to the sum of the fatigue service factors corresponding to all sub-cycle fluctuations plus the fatigue service factor corresponding to the main fluctuation of the transient. Specifically, based on the alternating stress intensity corresponding to the transient, the corresponding safe number of cycles is obtained from the material fatigue life curve of the relevant critical parts, and then the corresponding fatigue service factor is calculated.

[0036] If a critical component that does not meet the conditions causes a fatigue service factor greater than that caused by the recommended design transient under the transient, then the transient cannot be classified as a recommended design transient and must be processed using other transient classification methods. If the transient cannot be classified into any category in the transient design document, then the transient is treated as a newly created design transient category. Based on the historical log data of the nuclear power unit, the design transient of the newly created category is defined and fatigue damage is analyzed to obtain the corresponding number of safe cycles and the transient limit value used for judgment.

[0037] In one embodiment of the present invention, for unclassified transients containing sub-cycle fluctuations, the unclassifiable operational transients are classified and counted by assessing the fatigue damage to mechanical components caused by the sub-cycle transients, instead of searching for the cause of the sub-cycle transients. The theoretical basis comes from the Nuclear Island Mechanical Equipment Design Specification (RCCM Specification). The RCCM Specification stipulates that stress changes caused by transient sub-cycle fluctuations do not need to be paired with other transients; only the fatigue damage caused by the sub-cycle fluctuations alone needs to be considered. If the alternating stress intensity caused by the sub-cycle transient is lower than the material's fatigue limit, or the fatigue damage generated by the operational transient is less than the damage generated by the design transient, the influence of the sub-cycle transient can be ignored during the transient classification process. The transient classification and counting are then determined based on the main trend and cause of the transient.

[0038] In one embodiment of the present invention, see Figure 1 and Figure 2 Verification of classification recommendations includes the following steps:

[0039] Step (1): Based on the unit operation log, transient monitoring data, and transient design documents, obtain the classification suggestions for the transient.

[0040] Specifically, the main process is as follows: Ignore sub-cycle fluctuations in the operational transient, determine the cause of the operational transient based on the unit operation log, and then find the corresponding design transient in the design transient list; compare the operational transient monitoring data with the design transient limits. If the monitoring data meets the limit requirements, then this design transient is used as the initial classification suggestion.

[0041] Step (2): Establish a representative list of mechanical components (i.e. key parts) of the main circuit system.

[0042] For example, when the M310 nuclear power unit is a 900MWa pressurized water reactor unit, based on engineering judgment and experience feedback, the following representative mechanical component analysis list is established, including: the connection nozzle between the main pipeline hot pipe section and the RRA system, the connection nozzle between the main pipeline cold pipe section and the RCV system drain line, the reactor pressure vessel inlet nozzle, the reactor pressure vessel outlet nozzle, the geometric discontinuity area of ​​the main pump casing, the coolant inlet nozzle of the steam generator main loop, the steam generator lower head, the manhole bolts of the steam generator lower head, and the connection area between the steam generator lower head and the tube sheet.

[0043] Step (3): Calculate the alternating stress intensity of each mechanical component under unclassified transient action;

[0044] The main process is as follows: the stress of each mechanical component can be calculated using finite element method or other methods; the stress cyclic pairing and alternating stress intensity of each mechanical component are calculated with reference to the RCCM standard.

[0045] Step (iv): Extract the alternating stress intensity corresponding to the transient state of the sub-cycle.

[0046] The main process is as follows: The corresponding stress cycle pairing and alternating stress intensity are found based on the time of occurrence of the sub-cycle fluctuation transient. Typically, the sub-cycle fluctuation transient corresponds to the secondary stress cycle pairing and alternating stress intensity.

[0047] Step (5): Compare the alternating stress intensity corresponding to the sub-cycle transient of each mechanical component with the material fatigue limit. If the alternating stress intensity of each mechanical component is less than the material fatigue limit, the unclassified transient can be classified as the initially suggested design transient. If the alternating stress intensity corresponding to the sub-cycle transient of a mechanical component is greater than the material fatigue limit, the analysis described in step (6) needs to be carried out.

[0048] The main process is as follows: For each mechanical component, the alternating stress intensity corresponding to the sub-cycle transient is extracted according to step (iv) and compared with the material fatigue limit. The material fatigue limit can be obtained by referring to Appendix ZI of the RCCM specification. If the alternating stress intensity of each mechanical component is less than the material fatigue limit, it can be considered that the sub-cycle transient has not caused fatigue damage to the mechanical component, and the influence of the sub-cycle transient can be ignored. The operating transient is classified as the initial recommended design transient. During the transient statistics process, the occurrence number of the design transient is increased by one.

[0049] If the alternating stress intensity of a mechanical component exceeds the material fatigue limit, then the analysis work described in step (vi) needs to be carried out.

[0050] Step (VI): For the mechanical components identified in Step (V) that require further analysis, calculate the fatigue service factor caused by the unclassified transient and the design transient, respectively. If the fatigue service factor caused by the unclassified transient is less than the fatigue service factor caused by the design transient, then the unclassified transient can also be classified as the initially suggested design transient.

[0051] Specifically, referring to the RCCM standard, the fatigue service factor of the mechanical component under unclassified transient action and design transient action are calculated separately. The material fatigue life curve can be obtained by referring to Appendix ZI of the RCCM standard. If the fatigue service factor caused by the unclassified transient is less than the fatigue service factor caused by the design transient, then the unclassified transient can be classified as the initially recommended design transient. During the transient statistics process, the occurrence count of this design transient is increased by one.

[0052] The following detailed description of this embodiment will be provided using a specific example of the M310 nuclear power unit.

[0053] According to the transient design data of the M310 nuclear power unit, when the unit performs certain functions or operations, the temperature, pressure, and other parameters of the main loop system typically increase or decrease monotonically. However, during actual operation, due to some unexpected reasons, the temperature, pressure, and other parameters of the main loop system may exhibit sub-cycle fluctuations, making these operational transients unclassifiable as design transients. The main idea of ​​this example is to avoid searching for the cause of the sub-cycle transients and instead classify and count unclassifiable operational transients by assessing the fatigue damage to mechanical components caused by the sub-cycle transients. Based on the nuclear island mechanical equipment design specifications and RCCM specifications, the stress and fatigue damage of each mechanical component under operational transient conditions are calculated. If the alternating stress intensity caused by the sub-cycle transient is lower than the material's fatigue limit, or the fatigue damage generated by the operational transient is less than the damage generated by the design transient, the influence of the sub-cycle transient can be ignored. Then, the transient classification and counting are determined based on the main trend and cause of the operational transient. This example can be applied to handle unclassifiable transient problems in the main circuit system of the M310 unit, providing support for unit operation license renewal, periodic safety reviews, and other tasks. It features low computational complexity and ease of application, filling a gap in existing technology.

[0054] Suppose that during the depressurization process of a main circuit hydrostatic test of an M310 nuclear power unit, the pressure of the main circuit system unexpectedly fluctuates, causing this operational transient to be unclassifiable, and the transient number is 000. It is now necessary to process and analyze this unclassified transient. Table 1 shows the pressure and temperature changes of the main circuit system.

[0055] Table 1. Pressure and Temperature of the Main Loop System in Uncategorized Transient (Tran.000) Systems

[0056] Time Pressure Temperature min bar ℃ 0 2 60 60 160 60 120 160 60 150 80 60 165 120 60 180 60 60 195 80 60 240 2 60

[0057] Step (1): Based on the unit operation log, transient monitoring data, and transient design documents, provide initial design transient classification suggestions for unclassified transients containing sub-cycle fluctuations; specifically:

[0058] 1.1 Based on the unit's operation log, it can be determined that the unit is currently undergoing a main circuit cold water pressure test, and the corresponding design transient should be transient X. Table 2 shows the pressure and temperature changes of the main circuit system during the design transient.

[0059] Table 2. Design Transient (Tran.X) Main Loop System Pressure and Temperature

[0060] Time Pressure Minimum Temperature min bar ℃ 0 1 60 60 172 60 120 172 60 180 1 60

[0061] 1.2 Ignoring sub-loop transients, the runtime transient data is compared with the design transient limits, as shown in Table 3. The runtime transient data meets the limit requirements; therefore, the initial classification suggestion is transient X.

[0062] Table 3 Comparison of parameters between Tran.X and Tran.000

[0063] Tran.000 Limit value (Tran.X) Maximum pressure bar 160 172 pressure difference bar 158 171 Minimum temperature ℃ 60 60

[0064] Step (II): Establish a representative list of mechanical components for the main circuit system;

[0065] Specifically, the mechanical component analysis list includes: the main pipeline hot pipe section connecting nozzle to the RRA system, the main pipeline cold pipe section connecting nozzle to the RCV system drain line, the reactor pressure vessel (RPV) inlet nozzle, the reactor pressure vessel (RPV) outlet nozzle, the main pump casing geometric discontinuity area, the steam generator (SG) main loop coolant inlet nozzle, the steam generator (SG) lower head, the steam generator (SG) lower head manhole bolts, and the steam generator (SG) lower head tube sheet connection area.

[0066] Step (3): Calculate the alternating stress intensity of each mechanical component under unclassified transient action;

[0067] 3.1 The mechanical analysis model of each mechanical component is established using the finite element method, and the stress under unclassified transient action is calculated, as shown in Table 4.

[0068] Table 4. Stress (SINT) of each mechanical component under unclassified transient (Tran.000) conditions.

[0069]

[0070]

[0071] 3.2 The stress cycle pairing and alternating stress intensity of each mechanical component were calculated according to the requirements of the RCCM specification, as shown in Table 5, where Time_i and Time_j represent the time points that constitute the stress cycle pairing.

[0072] Table 5. Stress Cyclic Pairing and Alternating Stress Intensity (Salt) Caused by Unclassified Transients

[0073]

[0074] Step (iv): Extract the alternating stress intensity corresponding to the transient state of the sub-cycle.

[0075] 4.1 Compare the stress cycle pairing results with the sub-cycle transient occurrence time to determine the alternating stress intensity corresponding to the sub-cycle transient, and mark it in bold italics in Table 5.

[0076] Step (V): Compare the alternating stress intensity corresponding to the sub-cycle transient of each mechanical component with the material fatigue limit. If the alternating stress intensity of each mechanical component is less than the material fatigue limit, the unclassified transient can be classified as the initially suggested design transient. If the alternating stress intensity corresponding to a sub-cycle transient of a mechanical component is greater than the material fatigue limit, then the analysis work described in Step (VI) needs to be carried out. Specifically:

[0077] 5.1 According to the RCCM standard, the fatigue limit of low alloy steel is 86 MPa; the fatigue limit of stainless steel is 180 MPa; and the fatigue limit of bolts is 37 MPa.

[0078] 5.2 Comparing the alternating stress intensity corresponding to the transient state of the subcycle in Table 5 with the fatigue limit of the material, it can be found that, except for the inlet nozzle of the reactor pressure vessel, the alternating stress intensity of other mechanical components is less than the fatigue limit of the corresponding material.

[0079] 5.3 Further analysis of the reactor pressure vessel inlet nozzle is required.

[0080] Step (VI): For the mechanical components identified in Step (V) that require further analysis, calculate the fatigue service factor caused by the unclassified transient and the design transient, respectively. If the fatigue service factor caused by the unclassified transient is less than the fatigue service factor caused by the design transient, then the unclassified transient can also be classified as the initially suggested design transient. Specifically:

[0081] 6.1 Calculate the fatigue service factor of the reactor pressure vessel inlet nozzle under unclassified transient and design transient conditions according to RCCM specifications. The calculated fatigue service factor caused by the design transient is 4.6 × 10⁻⁶. -5 The fatigue use factor caused by unclassified transients is 3.7 × 10⁻⁶. -5 .

[0082] 6.2. By comparison, it can be found that the fatigue service factor caused by the unclassified transient is less than that of the design transient. Therefore, this operational transient can be classified as the initially suggested design transient, i.e., transient X. The occurrence count of transient X will be increased by one in the transient statistics.

[0083] This embodiment fills a gap in existing technology. The M310 nuclear power unit was designed and built in China in the early 1990s using technology imported from France. With the extension of its service life, some units have accumulated a considerable number of unclassified transients. Currently, there is no good method for handling these transients. This example can be applied to handle unclassified transients in the main loop system of the M310 unit, including sub-cycle fluctuations, providing support for unit operating license renewals, periodic safety reviews, and other work. It features low computational load and ease of application.

[0084] This invention also provides a transient classification processing system for nuclear power units, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the aforementioned transient classification processing method. The concept of this system embodiment is the same as the working process of the detection method in the above embodiments. Therefore, all contents of the above detection method embodiments are incorporated into this device embodiment by full reference, and will not be repeated here.

[0085] The transient classification and processing method and system provided by this invention avoids searching for the cause of subcycle transients. Instead, it classifies and counts unclassifiable operational transients by evaluating the fatigue damage to mechanical components caused by subcycle transients. Based on the nuclear island mechanical equipment design specifications and RCCM specifications, it calculates the stress and fatigue damage of each mechanical component under operational transient action. If the alternating stress intensity caused by subcycle transients is lower than the fatigue limit of the material, or the fatigue damage generated by operational transients is less than the damage generated by design transients, the influence of subcycle transients can be ignored. Then, the transient classification and counting are determined based on the main changing trend and cause of operational transients.

[0086] The above description is merely a preferred embodiment of the present invention and does not limit its patent scope. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, whether directly or indirectly applied to other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A transient classification processing method for nuclear power units, characterized in that, When classifying transients generated by nuclear power units, if the transients cannot be classified due to subcycle fluctuations, the subcycle fluctuations should be ignored first, and then a classification suggestion should be given for the transients based on the unit operation log, transient monitoring data and transient design documents. The classification recommendations are verified by the following steps: calculating the alternating stress intensity corresponding to each stress cycle of each key part of the nuclear power unit under the transient action; If the alternating stress intensity corresponding to each key component under sub-cycle fluctuation is less than the fatigue limit of the corresponding material, then the transient is classified as a recommended design transient. Otherwise, the fatigue service factor caused by the key components that do not meet the conditions is calculated under the transient and the recommended design transient, respectively. If the fatigue service factor caused by the transient is less than the fatigue service factor caused by the recommended design transient, then the transient is classified as a recommended design transient.

2. The transient classification processing method according to claim 1, characterized in that, Providing classification suggestions for the transients includes the following steps: First, ignore the sub-cycle fluctuations in the transient, determine the cause of the transient based on the nuclear power unit operation log, and then find the corresponding design transient in the design transient list; The monitoring data of the transient is compared with the limit value of the design transient. If the monitoring data meets the corresponding limit requirements, the design transient is used as the initial classification suggestion.

3. The transient classification processing method according to claim 1, characterized in that, The process for obtaining the alternating stress intensity of the key component under the transient action is as follows: The finite element method was used to establish mechanical analysis models for the corresponding key components; According to the RCCM specification, the stress cycle pairing and corresponding alternating stress intensity of the corresponding key parts under the transient state are obtained by calculation. Based on the time of occurrence of the transient neutron cycle fluctuation, the alternating stress intensity corresponding to the neutron cycle fluctuation can be further determined.

4. The transient classification processing method according to claim 1, characterized in that, The corresponding fatigue limit is obtained from the fatigue life curve of the corresponding material in the key parts, and the alternating stress intensity corresponding to the sub-cycle fluctuation of each key part is compared with the fatigue limit of the corresponding material. If the alternating stress intensity corresponding to the sub-cycle fluctuation of each key part is less than the fatigue limit of the corresponding material, the transient is classified as the suggested design transient, and the number of occurrences of the design transient is increased by one.

5. The transient classification processing method according to claim 2, characterized in that, The design transient limits include temperature change range limits, pressure change range limits, and temperature change rate limits. The monitoring data of the transient must all correspond to limits less than or equal to the design transient limits in order for the design transient to be used as an initial classification suggestion.

6. The transient classification processing method according to claim 1, characterized in that, The transient includes one or more sub-cycle fluctuations, and the fatigue use factor of the transient is equal to the sum of the fatigue use factors corresponding to all sub-cycle fluctuations plus the fatigue use factor corresponding to the main transient fluctuation.

7. The transient classification processing method according to claim 1, characterized in that, If the alternating stress intensity corresponding to each sub-cycle fluctuation in the critical component is less than the fatigue limit of the corresponding material, then the transient is classified as a recommended design transient.

8. The transient classification processing method according to claim 1, characterized in that, If a critical component that does not meet the conditions causes a fatigue service factor greater than that caused under the recommended design transient, then the transient cannot be classified as a recommended design transient and must be processed using other transient classification methods.

9. The transient classification processing method according to claim 8, characterized in that, If the transient cannot be classified into any category in the transient design file, then the transient will be created as a new design transient category. Based on the historical log data of the nuclear power unit, the design transients of the newly established category are defined and fatigue damage is analyzed to obtain the corresponding number of safe cycles and the transient limits used for judgment.

10. The transient classification processing method according to claim 4, characterized in that, When the number of transient statistics exceeds the number of design occurrences, the number of design occurrences needs to be updated, and it needs to be demonstrated that the critical components will not experience fatigue fracture failure under the new number of design occurrences.

11. The transient classification processing method according to claim 1, characterized in that, The key components include: the connection nozzle between the hot section of the main pipeline and the RRA system, the connection nozzle between the cold section of the main pipeline and the RCV system drain line, the reactor pressure vessel inlet nozzle, the reactor pressure vessel outlet nozzle, the geometric discontinuity area of ​​the main pump casing, the coolant inlet nozzle of the steam generator main loop, the steam generator lower head, the manhole bolts of the steam generator lower head, and the connection area between the steam generator lower head and the tube sheet.

12. A transient classification processing system for nuclear power units, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the transient classification processing method according to any one of claims 1 to 11.

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