An intelligent classification method for primary circuit transients in pressurized water reactor nuclear power plants

Abstract

The present invention discloses a method for intelligently classifying transients in the primary circuit of a pressurized water reactor nuclear power plant. The method comprises the following steps: listing the types of transients that occur during the operation of the primary circuit of the nuclear power plant; transients refer to the impact on the primary circuit materials caused by instantaneous changes in temperature or pressure; analyzing the influencing parameters behind the transients to screen out the thermodynamic characteristics of the transients, which include common characteristics and independent characteristics. Transients associated with at least one common characteristic are recorded as common transients, while transients not associated with any common characteristics are recorded as independent transients; transients are classified into common transients and independent transients based on the correlation of the common characteristics; common transients are classified according to the state of the common characteristics and then located to the final transient type using the independent characteristics, while independent transients are directly located to the final transient type using the independent characteristics. The intelligent method for classifying transients in the primary circuit provided by the present invention improves the speed and accuracy of primary circuit transient classification.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent transient classification of nuclear power plants, and in particular to an intelligent transient classification method for a primary circuit of a pressurized water reactor nuclear power plant. Background Art

[0002] During nuclear power plant operation, the integrity of the reactor's primary pressure boundary must be maintained. Pipes, vessels, and other equipment in the primary circuit operate under high temperatures, high pressures, and high levels of radioactivity. Their temperatures and pressures fluctuate with operating conditions. Temperature fluctuations can cause metal materials to contract or expand, generating thermal stress and fatigue. Pressure fluctuations can also induce internal stresses in metal materials, leading to mechanical fatigue in addition to strength damage. Transients are short-term changes in temperature or pressure that cause shock to primary circuit materials. Analyzing, classifying, and compiling statistics on the number and intensity of these changes is known as transient statistics.

[0003] Transient statistics are primarily divided into three steps: identification, classification, and organization. Identification involves continuous monitoring of key parameters of a circuit according to the thresholds specified in the design documents. A transient is identified when a key parameter changes beyond the threshold. Classification involves categorizing the transient as a design transient based on the unit's state or operating conditions at the time of the transient. For the M310 pressurized water reactor nuclear power unit, there are seven major categories and 135 types of transients. These include normal operating conditions, medium-frequency accident conditions, abnormal conditions, extremely low-probability accident conditions, injection systems, hydrostatic tests, pressurizer SEBIM valve tests, and unclassified transients. Organization involves organizing all recorded transients and compiling reports for archiving according to the plant's prescribed cycle (annually or per fuel cycle).

[0004] Currently, transient classification is primarily done manually. This is accomplished by comprehensively assessing the unit's operating status or operation, analyzing curve changes and threshold breaches, and incorporating the experience of past transient engineers.

[0005] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above content has been disclosed before the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of this application. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the present invention provides a method for intelligently classifying transients in the primary circuit of a pressurized water reactor nuclear power plant. The specific technical solution is as follows:

[0007] A method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant is provided, comprising the following steps:

[0008] List the types of transients that occur during the operation of the primary circuit of a nuclear power plant; transients refer to the impact on the primary circuit materials caused by instantaneous changes in temperature or pressure;

[0009] The influencing parameters behind the transients are analyzed to screen out thermodynamic characteristics of the transients, wherein the thermodynamic characteristics include common characteristics and independent characteristics, wherein the common characteristics include one or more of the unit thermal power status, the unit overhaul status, and the fuel extension period status, and the common characteristics are associated with more than 70% of the transient types. Transients associated with at least one of the common characteristics are recorded as common transients, and transients not associated with any of the common characteristics are recorded as independent transients. The transients are divided into common transients and independent transients after correlation screening of the common characteristics. After the common transients are classified by the status of the common characteristics, the independent characteristics are used to locate the final transient type, while the independent transients are directly located to the final transient type by the independent characteristics.

[0010] Furthermore, the unit thermal power status includes thermal power rising, thermal power falling, thermal power remaining unchanged and being a non-zero value, and thermal power being a zero value; the unit overhaul status includes being in unit overhaul and not being in unit overhaul; the fuel extension period status includes being in an extension period and not being in an extension period; and based on the correlation and status relationship between the common transients and the common features, the classification results are preliminarily grouped, with each group corresponding to one or more independent features.

[0011] Furthermore, after the common transients are initially classified according to the common feature states, the corresponding groups are associated with one or more independent features. At this time, if the common transients meet the state requirements of a preset associated independent feature, they will be mapped to a transient type accordingly.

[0012] Furthermore, the independent features include one or more of the hot leg temperature state, the cold leg temperature state, the transient degree of thermal power, the number of intermediate platforms, the degree of change of the primary circuit pressure, the valve state, and the secondary circuit pressure change.

[0013] Furthermore, if the state of the common feature corresponding to the common transient is as follows:

[0014] If the unit thermal power increases, is not related to the unit overhaul, is not related to the fuel extension period, and the unit thermal power increases in a step-like manner, then the transient type is: instantaneous increase in unit load;

[0015] If the thermal power of the unit decreases, is not related to the unit overhaul, is not related to the fuel extension period, and the thermal power of the unit decreases in a step-like manner, then the transient type is defined as: instantaneous reduction in unit load.

[0016] If the unit thermal power is 0, the unit is undergoing overhaul, and is not in a fuel extension period, and the hot leg temperature rises and the initial temperature is greater than a preset value, and the number of intermediate platforms is less than 6, then the transient type is: from RRA cooling shutdown mode to hot shutdown mode after the reactor cover is opened;

[0017] If the unit thermal power is 0, the unit is not undergoing overhaul or fuel extension, and the hot leg temperature rises and the initial temperature is greater than the preset value, and the number of intermediate platform times is less than 6, then the transient type is: the reactor goes from RRA cooling shutdown mode to hot shutdown mode without opening the reactor cover.

[0018] If the unit thermal power increases, the unit is not undergoing overhaul, and is not in a fuel extension period, and the hot leg temperature increases synchronously with the thermal power, and the cold leg temperature fluctuates around a preset temperature, the transient type is defined as a normal increase in stack power between 15% and 100%.

[0019] If the unit thermal power increases, the unit is not undergoing overhaul, and is not in a fuel extension period, and the hot leg temperature increases synchronously with the thermal power and the cold leg temperature continues to increase, the transient type is classified as an abnormal increase in stack power between 15% and 100%.

[0020] If the unit thermal power decreases, the unit is not undergoing overhaul, and is not in a fuel extension period, and the cold leg temperature remains unchanged and the hot leg temperature decreases synchronously with the thermal power, the transient type is defined as a normal decrease in stack power between 15% and 100%.

[0021] If the unit thermal power decreases, the unit is not in overhaul, and is not in a fuel extension period, and the cold leg temperature continues to decrease, the transient type is classified as an abnormal decrease in stack power between 15% and 100%.

[0022] Furthermore, the independent transient is an RCV transient, and its corresponding independent feature is a relative change of the RCV system with respect to the RCP system. The RCV transient is further classified into different transient types according to different preset intervals of the relative change.

[0023] Furthermore, the relative change of the RCV system relative to the RCP system is |ΔT RCV -ΔT RCP |, where

[0024] ΔT RCV =T RCV2 -T RCV1

[0025] ΔT RCP =T RCP2 -T RCP1

[0026] Where, T RCV1 is the value at the beginning of transient change of the measurement point of the RCV system, T RCV2 is the transient end value of the RCV system measurement point, T RCP1 is the value at which the transient starts at the measurement point of the RCP system, T RCP2 It is the value at the end of transient of the measurement point of the RCP system.

[0027] Compared with the existing technology, the present invention has the following advantages: instead of identifying and classifying transients through traditional methods such as comparing monitoring curves one by one, reading daily reports, or using threshold panes, the unit status and key parameters are screened and classified according to thermodynamic characteristics, greatly improving the classification speed and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1. It is a schematic diagram of an independent transient classification framework in a method for intelligently classifying transients in a primary circuit of a pressurized water reactor nuclear power plant provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and the accompanying drawings are used to distinguish similar items and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the present invention described herein can be implemented in sequences other than those illustrated or described herein. Furthermore, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions.

[0031] In one embodiment of the present invention, a method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant is provided, comprising the following steps:

[0032] List the types of transients that occur during the operation of the primary circuit of a nuclear power plant. See Table 1 for a list of transient types. The transient refers to the impact on the primary circuit materials caused by the instantaneous change of temperature or pressure.

[0033] Table 1 List of some transient types

[0034]

[0035]

[0036] The influencing parameters behind the transients are analyzed to identify the thermodynamic characteristics of the transients. Thermodynamic characteristics refer to the use of parameters such as temperature, pressure, and flow rate behind the transients to identify the thermodynamic relationships of all transients. These thermodynamic characteristics include common characteristics and independent characteristics. Common characteristics include one or more of the following: unit thermal power status, unit overhaul status, and fuel extension status. The fuel extension status is used to identify transients related to extended operation. Changes in other parameters such as temperature and pressure can be defined as independent characteristics. Independent characteristics are independent characteristic fields for each transient.

[0037] The common features have an associated impact on more than 70% of the transient types, wherein transients associated with at least one of the common features are recorded as common transients, and transients that are not associated with any of the common features are recorded as independent transients; the transients are divided into common transients and independent transients after being screened for association with the common features; the common transients are classified by the state of the common features and then located to the final transient type using the independent features, while the independent transients are directly located to the final transient type through the independent features.

[0038] The unit thermal power status includes thermal power rising, thermal power falling, thermal power remaining unchanged and being a non-zero value, and thermal power being a zero value; the unit overhaul status includes being in unit overhaul and not being in unit overhaul; the fuel extension period status includes being in an extension period and not being in an extension period; based on the correlation and status relationship between the common transients and the common features, the classification results are preliminarily grouped, with each group corresponding to one or more independent features.

[0039] After the common transients are initially classified according to the common feature states, the corresponding groups are associated with one or more independent features. At this time, if the common transients meet the state requirements of a preset associated independent feature, they will be mapped to a transient type accordingly.

[0040] The independent features include one or more of the following: hot leg temperature state, cold leg temperature state, transient degree of thermal power, number of intermediate platforms, degree of change of primary circuit pressure, valve state, and secondary circuit pressure change.

[0041] If the state of the common feature corresponding to the common transient is as follows:

[0042] If the unit thermal power increases, is not related to the unit overhaul, is not related to the fuel extension period, and the unit thermal power increases in a step-like manner, then the transient type is: instantaneous increase in unit load;

[0043] If the thermal power of the unit decreases, is not related to the unit overhaul, is not related to the fuel extension period, and the thermal power of the unit decreases in a step-like manner, then the transient type is defined as: instantaneous reduction in unit load.

[0044] If the unit thermal power is 0, the unit is undergoing overhaul, and is not in a fuel extension period, and the hot leg temperature rises and the initial temperature is greater than a preset value, and the number of intermediate platforms is less than 6, then the transient type is: from RRA cooling shutdown mode to hot shutdown mode after the reactor cover is opened;

[0045] If the unit thermal power is 0, the unit is not undergoing overhaul or fuel extension, and the hot leg temperature rises and the initial temperature is greater than the preset value, and the number of intermediate platform times is less than 6, then the transient type is: the reactor goes from RRA cooling shutdown mode to hot shutdown mode without opening the reactor cover.

[0046] If the unit thermal power increases, the unit is not undergoing overhaul, and is not in a fuel extension period, and the hot leg temperature increases synchronously with the thermal power, and the cold leg temperature fluctuates around a preset temperature, the transient type is defined as a normal increase in stack power between 15% and 100%.

[0047] If the unit thermal power increases, the unit is not undergoing overhaul, and is not in a fuel extension period, and the hot leg temperature increases synchronously with the thermal power and the cold leg temperature continues to increase, the transient type is classified as an abnormal increase in stack power between 15% and 100%.

[0048] If the unit thermal power decreases, the unit is not undergoing overhaul, and is not in a fuel extension period, and the cold leg temperature remains unchanged and the hot leg temperature decreases synchronously with the thermal power, the transient type is defined as a normal decrease in stack power between 15% and 100%.

[0049] If the unit thermal power decreases, the unit is not in overhaul, and is not in a fuel extension period, and the cold leg temperature continues to decrease, the transient type is classified as an abnormal decrease in stack power between 15% and 100%.

[0050] Table 2 Thermodynamic characteristics of some transients

[0051]

[0052]

[0053]

[0054]

[0055] Among them, for the concepts of rise, fall, step, etc. mentioned in the thermodynamic characteristics, when the valve state corresponding to the measuring point is open, the time series data is 1, and when it is closed, the time series data is 0; rise means that the first-order derivative of the time series data fitting curve is greater than 0 within the definition domain (that is, the time period when the transient occurs); fall means that the first-order derivative of the time series data fitting curve is less than 0 within the definition domain (that is, the time period when the transient occurs); significant rise means that the first-order derivative of the time series data fitting curve is greater than 1 within the definition domain (that is, the time period when the transient occurs); significant fall means that the first-order derivative of the time series data fitting curve is less than -1 within the definition domain (that is, the time period when the transient occurs).

[0056] According to the thermodynamic characteristics, the above classification method is programmed and the classification of the first and second type transients (i.e., common transients) of a certain unit is given as an example:

[0057] 1) Select a transient data file that has been cleaned and cut, and convert it to JSON format;

[0058] 2) The start and end times of recent power plant overhauls and fuel extension operation time have been completed in the program for use in calculations;

[0059] 3) Import the data into the classification program and start the calculation;

[0060] 4) Determine the data time, the result is the daily period without major maintenance (the first judgment of the common field);

[0061] 5) Determine the trend of thermal power in the data, which is an increase (the second determination of the common field);

[0062] 6) Determine the thermal power value at the end of transient: greater than 15% (determine the first independent field);

[0063] 7) Determine whether the start and end time of the transient overlap with the fuel extension period: No overlap (third judgment of the common field);

[0064] 8) Determine the temperature change of the cold leg: basically unchanged, that is, the first-order derivative of its function fluctuates around 0 (determine the second independent field);

[0065] 9) Determine the temperature change of the hot leg: the hot leg temperature rises synchronously with the thermal power (determine the third independent field);

[0066] 10) Draw the conclusion: The thermodynamic characteristics of the transient numbered 3.1 are met, and the transient type is obtained accordingly;

[0067] 11) Engineers check the results and the results are correct;

[0068] 12) The process ends.

[0069] In one embodiment of the present invention, the independent transient is an RCV transient, and its corresponding independent characteristic is the relative change of the RCV system relative to the RCP system, see Figure 1 , according to different preset intervals of relative change, the RCV transient is further classified into different transient types. Specifically, the relative change of the RCV system relative to the RCP system is |ΔT RCV -ΔT RCP |, where

[0070] ΔT RCV =T RCV2 -T RCV1

[0071] ΔT RCP =T RCP2 -T RCP1

[0072] Where, T RCV1 is the value at the beginning of transient change of the measurement point of the RCV system, T RCV2 is the transient end value of the RCV system measurement point, T RCP1 is the value at which the transient starts at the measurement point of the RCP system, T RCP2 is the value at the end of transient change of the measuring point of the RCP system, and Δ represents the amount of change.

[0073] Since RCV transients are independent transients, their occurrence is not related to the unit's power, overhaul, fuel extension period, etc. Therefore, RCV-related transients do not require the calculation results of common fields to be determined, but only the calculation results of independent fields to be determined. The following example illustrates this:

[0074] 1) Select a transient data file that has been cleaned and cut, and convert it to JSON format;

[0075] 2) Verify the start and end data of the RCV system and RCP system;

[0076] 3) Calculate the relative change of the RCV system relative to the RCP system, and the result is 25;

[0077] 4) Verify the relative change according to the RCV system transient logic diagram to obtain the classification result;

[0078] 5) Draw the conclusion: The thermodynamic characteristics of the transient numbered 33 are met, and the transient type is obtained accordingly;

[0079] 6) Engineers check the classification results: the results are correct;

[0080] 7) The process ends.

[0081] The intelligent classification method for primary circuit transients in pressurized water reactor nuclear power plants, provided by this invention, intelligently categorizes input data (i.e., transient data) in a given format according to the design transient types of the pressurized water reactor nuclear power plant. For results that can be determined, the classification results are directly output. For results that cannot be determined, an alarm is issued, requiring manual intervention and inspection.

[0082] The intelligent classification method for primary-loop transients in pressurized water reactor nuclear power plants provided by the present invention realizes automatic classification of transients, eliminating the need for engineers to identify and classify transients through traditional methods such as comparing monitoring curves one by one, reading daily reports, or using threshold panes. Engineers can screen unit status and key parameters according to thermodynamic characteristics, and can also develop relevant computer software to achieve fully automatic operation.

[0083] The above description is only a preferred embodiment of the present invention and does not limit the scope of the patent. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of the present invention, directly or indirectly applied in other related technical fields, is also included in the scope of patent protection of the present invention.

Claims

1. A method for intelligently classifying transients in the primary circuit of a pressurized water reactor nuclear power plant, characterized in that: The following steps are involved: List the types of transients that occur during the operation of the primary circuit of a nuclear power plant; transients refer to the impact on primary circuit materials caused by instantaneous changes in temperature or pressure; The influencing parameters behind the transients are analyzed to screen out thermodynamic characteristics of the transients, wherein the thermodynamic characteristics include common characteristics and independent characteristics, wherein the common characteristics include one or more of the unit thermal power status, the unit overhaul status, and the fuel extension period status, and the common characteristics are associated with more than 70% of the transient types. Transients associated with at least one of the common characteristics are recorded as common transients, and transients not associated with any of the common characteristics are recorded as independent transients. The transients are divided into common transients and independent transients after correlation screening of the common characteristics. After the common transients are classified by the status of the common characteristics, the independent characteristics are used to locate the final transient type, while the independent transients are directly located to the final transient type by the independent characteristics.

2. The method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The unit thermal power status includes thermal power rising, thermal power falling, thermal power remaining unchanged and being a non-zero value, and thermal power being a zero value; the unit overhaul status includes being in unit overhaul and not being in unit overhaul; the fuel extension period status includes being in an extension period and not being in an extension period; based on the correlation and status relationship between the common transients and the common features, the classification results are preliminarily grouped, with each group corresponding to one or more independent features.

3. The method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant according to claim 1, characterized in that: After the common transients are initially classified according to the common features, the corresponding groups are associated with one or more independent features. If the common transients meet the state requirements of a preset associated independent feature, they will be mapped to a transient type accordingly.

4. The method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant according to claim 2, characterized in that: The independent features include one or more of the following: hot leg temperature state, cold leg temperature state, transient degree of thermal power, number of intermediate platforms, degree of change of primary circuit pressure, valve state, and secondary circuit pressure change.

5. The method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant according to claim 4, characterized in that: If the state of the common feature corresponding to the common transient is as follows: If the unit thermal power state increases, is not related to the unit overhaul, is not related to the fuel extension period, and the unit thermal power state is a step-up type, then the transient type is: instantaneous increase in unit load; If the thermal power state of the unit decreases, is not related to the unit overhaul, is not related to the fuel extension period, and the thermal power state of the unit is a step-down type, then the transient type is: instantaneous reduction of unit load.

6. The method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant according to claim 5, characterized in that: If the unit thermal power state is 0, the unit is under overhaul, and is not in the fuel extension period, and the hot leg temperature state rises and the starting temperature is greater than the preset value, and the number of intermediate platforms is less than 6, then the transient type is: from RRA cooling shutdown mode to hot shutdown mode after the reactor cover is opened; If the unit thermal power state is 0, the unit is not undergoing overhaul, and the unit is not in a fuel extension period, and the hot leg temperature state rises with the starting temperature greater than the preset value and the number of intermediate platform times is less than 6, then the transient type is: the reactor is not uncovered and changes from RRA cooling shutdown mode to hot shutdown mode.

7. The method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant according to claim 5, characterized in that: If the unit thermal power state increases, the unit is not in overhaul, and is not in a fuel extension period, and the hot leg temperature state increases synchronously with the thermal power, and the cold leg temperature state fluctuates relative to the preset temperature, then the transient type is set as: normal increase in stack power between 15% and 100%; If the unit's thermal power status increases, the unit is not undergoing overhaul, and is not in a fuel extension period, and the hot leg temperature status increases synchronously with the thermal power, and the cold leg temperature status continues to increase, then the transient type is defined as an abnormal increase in stack power between 15% and 100%.

8. The method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant according to claim 5, characterized in that: If the unit thermal power state decreases, the unit is not undergoing overhaul, and is not in a fuel extension period, and the cold leg temperature state remains unchanged, and the hot leg temperature state decreases synchronously with the thermal power, then the transient type is set as a normal decrease in stack power between 15% and 100%; If the unit thermal power state decreases, is not in the unit overhaul, is not in the fuel extension period, and the cold leg temperature state continues to decrease, the transient type is: abnormal decrease in stack power between 15% and 100%.

9. The method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The independent transient is an RCV transient, and its corresponding independent feature is the relative change of the RCV system with respect to the RCP system. The RCV transient is further classified into different transient types according to different preset intervals of the relative change.

10. The method for intelligently classifying primary circuit transients in a pressurized water reactor nuclear power plant according to claim 9, characterized in that: The relative change of the RCV system relative to the RCP system is |ΔT RCV -ΔT RCP |, where ΔT RCV =T RCV2 -T RCV1 ΔT RCP =T RCP2 -T RCP1 Where, T RCV1 is the value at which the transient starts at the measurement point of the RCV system, T RCV2 is the value at the end of transient change of the measurement point of the RCV system, T RCP1 is the value at which the transient starts at the measurement point of the RCP system, T RCP2 It is the value at the end of transient change of the measurement point of the RCP system.

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