Method for evaluating consequences of pipe failure in nuclear power plant based on internal water flooded psa

Abstract

The application discloses a nuclear power plant pipeline failure consequence evaluation method based on internal water-flooded PSA, and comprises the following steps: obtaining pipeline parameters of a target pipeline, taking the target pipeline as a water-flooded source, determining affected structures, systems or components after water-flooding and water-flooding propagation paths; performing water-flooding scenario analysis and water-flooding consequence analysis, determining direct and indirect influences caused by target pipeline failure, and realizing qualitative analysis of target pipeline failure consequences; based on the results of the qualitative analysis, performing quantitative analysis of the target pipeline failure consequences, calculating a core damage condition probability and a radioactive early release condition probability, determining a target pipeline failure consequence level, and completing pipeline failure consequence evaluation. The application realizes qualitative analysis of pipeline failure consequences by dividing water-flooded areas after pipeline failure, analyzing water-flooding scenarios, analyzing water-flooding consequences and analyzing break isolation possibilities, and then obtains accurate quantitative values of pipeline failure consequences, thereby improving the accuracy of pipeline failure consequence evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant pipelines, and in particular to a nuclear power plant pipeline failure consequence assessment method based on internal flooding PSA. Background Art

[0002] During the operating life of a nuclear power plant, equipment and components are subject to a variety of factors, including stress, temperature, radiation, hydrogen adsorption, corrosion, vibration, and wear. These factors can lead to aging, embrittlement, fatigue, and defects, degrading material properties and ultimately causing cracks, leaks, and ruptures. These conditions can affect component operation and ultimately plant safety. The consequences of these conditions are directly related to the service life of the equipment or components and are difficult to predict. Therefore, it is necessary to inspect the metal condition of nuclear safety Level 1, 2, and 3 pressure-bearing equipment and piping, known as in-service inspections (ISIs), to promptly identify new defects and track the spread of known defects. This helps determine whether the equipment or components remain acceptable for safe plant operation and whether remedial measures are necessary. In fact, nuclear safety regulators require nuclear power plant owners to develop and implement an ISI program, which has become part of the nuclear power plant licensing benchmark. This program ensures regular inspections of systems and components throughout the plant's operating life to identify potential damage and defects and determine whether the plant continues to meet safe operation requirements.

[0003] Currently, in-service inspections (ISIs) for operating nuclear power plants in China are conducted based on deterministic stress analysis, expert judgment, and operational experience. For example, these are developed in accordance with the requirements of the American Society of Mechanical Engineers' Boiler and Pressure Vessel Code, Section XI (ASME BPVC XI), while adhering to nuclear safety regulations and guidelines. However, these routine ISI analysis processes are often conservative and fail to accurately account for the potential for pipeline failure. In fact, over 2,000 reactor-years of nuclear power plant operating experience demonstrate that pipeline failures are primarily caused by corrosion and fatigue, and that equipment or pipeline failures often occur in areas outside the scope of the plant's routine in-service inspection procedures.

[0004] With the nuclear industry's summary of the ISI (In-Service Inspection) of nuclear power plant pipelines and the development of the application of the Probabilistic Safety Assessment (PSA) method for internal flooding, a set of risk-informed pipeline in-service inspection methods (RI-ISI) has now been formed. This method comprehensively considers the risk insights of PSA and traditional engineering analysis conclusions, optimizes the utilization of ISI resources, and is one of the successful applications of risk-informed decision-making technology in nuclear power plants.Figure 1 As shown in Figure 1, existing risk-based in-service inspections (RI-ISI) primarily include pipeline failure consequence assessment, pipeline failure probability analysis (including pipeline degradation mechanism analysis), pipeline segment risk classification, inspection unit selection, and risk impact assessment. Pipeline failure consequence assessment is the primary task and one of the key elements of RI-ISI. Therefore, evaluating the consequences of pipeline failure is crucial.

[0005] However, the existing pipeline failure consequence assessment method does not take into account comprehensive factors and only considers the severity of the failure consequence according to the safety level of the pipeline, resulting in inaccurate pipeline failure consequence assessment. Summary of the Invention

[0006] To address the deficiencies of the above-mentioned prior art, the present invention provides a nuclear power plant pipeline failure consequence assessment method based on internal flooding PSA. Based on the internal flooding probabilistic safety assessment method, this method achieves accurate assessment of pipeline failure consequences in RI-ISI. Specifically, by dividing the flooded area after pipeline failure, analyzing the flooding scenario, analyzing the flooding consequences, and analyzing the possibility of breach isolation, a qualitative analysis of the pipeline failure consequences is achieved. This is then quantified to obtain accurate quantitative values ​​of the pipeline failure consequences, achieving an accurate assessment of the pipeline failure consequences. This helps improve the efficiency and accuracy of risk-based pipeline in-service inspection (RI-ISI).

[0007] In a first aspect, the present disclosure provides a method for evaluating the consequences of nuclear power plant pipeline failure based on internal flooding PSA:

[0008] A method for nuclear power plant piping failure consequence assessment based on internal flooding PSA, including:

[0009] Obtaining pipeline parameters of a target pipeline, where the target pipeline is any pipeline among the multiple pipelines to be evaluated;

[0010] Taking the target pipeline as the flood source, determine the systems or components affected by the flood and the flooding spread path;

[0011] Conduct flooding scenario analysis and flooding consequence analysis to determine the direct and indirect impacts of target pipeline failure and achieve qualitative analysis of the consequences of target pipeline failure;

[0012] Based on the results of qualitative analysis, the consequences of target pipeline failure are quantitatively analyzed, the conditional probability of core damage and the conditional probability of early radioactive release are calculated, the level of target pipeline failure consequences is determined, and the pipeline failure consequence assessment is completed.

[0013] A further technical solution is to determine the structures, systems and components affected by the target pipeline flooding based on the spatial positions and equipment elevations of each structure, system and component determined in the internal flooding PSA qualitative analysis, as well as the possibility of each structure, system and component being affected by splashing, local flooding and major flooding and their corresponding mitigation facilities.

[0014] A further technical solution is that the structures, systems or components affected by the flooding include equipment modeled in the internal flooding PSA model, that is, equipment affected by the flooding and having an impact on the risk of the power plant; and also include equipment not modeled in the internal flooding PSA model, that is, equipment that is easily affected by the flooding and whose failure will affect the normal operation of the power plant.

[0015] A further technical solution is to determine the flooding spread path after the target pipeline fails based on the specific layout of the nuclear power plant and the flooding mitigation facilities.

[0016] As a further technical solution, the flooding scenario analysis specifically refers to establishing a flooding damage decision tree according to different failure conditions of the target pipeline and classifying different flooding damage states.

[0017] In a further technical solution, the process of establishing the flood damage decision tree is as follows:

[0018] When the target pipeline fails, different flooding scenarios are first classified according to the target pipeline pressure boundary failure type, including: spraying, local flooding, and major flooding;

[0019] Then, for different flooding scenarios, different flooding damage states are divided according to whether isolation is carried out before the loss of the circulating water system function, whether isolation is carried out before the loss of structures, systems or components requiring circulating water cooling, and whether the core is damaged.

[0020] A further technical solution is that the flood consequence analysis includes determining the flood spreading path and mitigation information of the power plant, calculating the maximum flooding water level, evaluating the impact of the flooding on important structures, systems or components of the power plant, and identifying the initiating events that caused it.

[0021] A further technical solution is to convert the qualitative analysis into quantitative analysis by modifying the relevant initiating events and basic events based on the existing flooding PSA model through qualitative analysis of flooding scenario analysis and flooding consequence analysis.

[0022] In a second aspect, the present disclosure further provides an electronic device comprising a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the steps of the method described in the first aspect are completed.

[0023] In a third aspect, the present disclosure further provides a computer-readable storage medium for storing computer instructions, which, when executed by a processor, complete the steps of the method described in the first aspect.

[0024] One or more of the above technical solutions have the following beneficial effects:

[0025] This paper proposes a nuclear power plant pipeline failure consequence assessment method based on internal flooding PSA. Building on existing internal flooding probabilistic safety assessment methods, this method qualitatively analyzes the consequences of pipeline failure by dividing the flooded area after pipeline failure, analyzing the flooding scenario, the flooding consequences, and the possibility of breach isolation. This method then quantifies the consequences and obtains accurate quantitative values ​​for the consequences. This method enables accurate assessment of the consequences of pipeline failure, helping to improve the efficiency and accuracy of risk-based pipeline in-service inspections (RI-ISI). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 A flowchart of the existing risk-based pipeline in-service inspection methodology;

[0028] Figure 2 A flowchart of the existing internal flooding probabilistic safety assessment method;

[0029] Figure 3 This is a flow chart of the method described in Example 1 of the present invention;

[0030] Figure 4 A schematic diagram of a flooding spread path constructed in accordance with the first embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the structure of the flood damage decision tree described in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] Example 1

[0035] This embodiment provides a method for evaluating the consequences of nuclear power plant pipeline failure based on internal flooding PSA, such as Figure 3 As shown, the following steps are included:

[0036] Obtaining pipeline parameters of a target pipeline, where the target pipeline is any pipeline among the multiple pipelines to be evaluated;

[0037] Taking the target pipeline as the flood source, determine the structures, systems and components affected by the flood, as well as the flood spread path;

[0038] Conduct flooding scenario analysis and flooding consequence analysis to determine the direct and indirect impacts of target pipeline failure and achieve qualitative analysis of the consequences of target pipeline failure;

[0039] Based on the results of qualitative analysis, the consequences of target pipeline failure are quantitatively analyzed, the conditional probability of core damage and the conditional probability of early radioactive release are calculated, the level of target pipeline failure consequences is determined, and the pipeline failure consequence assessment is completed.

[0040] In this embodiment, based on the existing internal flooding probabilistic safety assessment (PSA) method, an accurate assessment of the consequences of pipeline failure is achieved.

[0041] like Figure 2 As shown, based on the internal flooding PSA method, the flooded area is first identified and divided. The flooded area is the basic unit of internal flooding PSA analysis and is defined as a part of a building or power plant that is separated from other areas by a flood barrier sufficient to prevent flooding. Within the same flooded area, flooding has similar impacts on the power plant. The division of flooded areas generally considers three aspects:

[0042] (1) Flooding sources and flooding mechanisms;

[0043] (2) The flooding may affect the SSCs (structures, systems and components), cause the failure of certain mitigation systems or equipment, or / and lead to an initiating event;

[0044] (3) Path of flooding.

[0045] By considering the above three factors, the flooded area is divided. Based on the above ideas, in this embodiment, the pipeline parameters of the target pipeline, such as pipeline distribution information, are first obtained. The target pipeline is any one of the multiple pipelines to be evaluated. Unlike the internal flooding PSA, the pipeline to be evaluated in the pipeline failure consequence assessment is a potential flooding source, so there is no need to identify the flooding source in the area. Therefore, the target pipeline is used as the flooding source to determine the structures, systems and components affected by the flooding of the target pipeline, as well as the flooding spread path, and then the flooded area involved in the target pipeline as the flooding source is identified and determined.

[0046] Determining the affected structures, systems, and components (SSCs) and flooding paths of target pipeline flooding requires consideration of multiple factors. These SSCs include not only the equipment modeled in the PSA (i.e., equipment affected by flooding and impacting power plant risk), but also critical equipment not modeled in the internal flooding PSA model that is susceptible to flooding and whose failure would affect normal power plant operations. As the source of the flooding changes, the affected SSCs, or equipment, will also change.

[0047] That is to say, it is necessary to determine the structures, systems and components affected by the target pipeline flooding based on the spatial location and equipment elevation of each structure, system and component determined in the internal flooding PSA qualitative analysis, as well as the possibility of each structure, system and component being affected by splashing, local flooding and major flooding and their corresponding mitigation facilities, such as barriers, flooding or sprinkler protection capacity levels.

[0048] At the same time, according to the specific layout of the nuclear power plant and flooding mitigation facilities such as waterproof sills, spray covers and floor drains, the flooding spread path after the target pipeline fails is determined, such as Figure 4 In a flood spreading path diagram, water flows from flooded area 40356 to flooded area 40352 through a door, and flooded area 40352 flows through a door to flooded area 40350, and so on.

[0049] After identifying multiple flooded areas with the target pipeline as the flooding source, a qualitative analysis is conducted on each flooded area. Specifically, this involves conducting a flooding scenario analysis and a flooding consequence analysis to determine the direct and indirect impacts caused by the failure of the target pipeline and to qualitatively analyze the consequences of the target pipeline failure.

[0050] At this point, it is important to clarify that the pipeline failure consequence assessment focuses primarily on the impact of the target pipeline failure on power plant operations. This impact may be direct, indirect, or a combination of both. A direct impact refers to the loss of a series or system and possible associated diversions, or the triggering of an initiating event such as a loss of coolant accident (LOCA). An indirect impact involves flooding, spraying, or pipe whipping, spatially impacting nearby structures, systems, and components, or causing water tank depletion and the loss of the systems it supports.

[0051] That is to say, the initiating event directly caused by the failure of the target pipeline is the direct impact, such as the rupture of the injection line connected to the main pipeline of a certain circuit, the initiating event caused by it, namely the rupture of the injection line, is a direct impact; and the initiating event indirectly caused by the failure of the target pipeline is the indirect impact, such as the flooding, spraying and pipeline impact on equipment near the rupture caused by the failure of the pipeline of a certain circuit are indirect impacts.

[0052] In fact, for the flooded area where the breach is located, that is, the flooded area where the flooding source is located, there may be direct impact and indirect impact. For the area where there is no breach, that is, the flooded area where there is no flooding source, there is only indirect impact.

[0053] When conducting a qualitative assessment of the consequences of pipeline failure, it is necessary to conduct a comprehensive assessment of a series of pipeline failures with direct and indirect impacts, and clearly distinguish between the consequences caused by direct impacts and the consequences caused by indirect impacts.

[0054] For a flooded area where the target pipeline is the source of flooding, that is, the flooded area where the source is located, the failure of the target pipeline is considered as the sole source of water, and only the flooding scenario caused by this source is considered. Flooding scenario analysis specifically involves establishing a flood damage decision tree based on the different failure conditions of the target pipeline, and classifying different flood damage states. In this case, the analysis of the flooded area includes both direct and indirect impacts caused by the flooding.

[0055] Flooding decision tree is an analytical method used in flooding PSA, such as Figure 5 As shown, the flood damage decision tree is established as follows: When a target pipeline fails, different flooding scenarios are first classified based on the target pipeline pressure boundary failure type, which includes spraying, localized flooding, and major flooding. Then, for each flooding scenario, the potentially affected equipment and whether flood isolation was successful are determined. Specifically, different flood damage states are classified based on whether isolation was achieved before the loss of circulating water system functionality, whether isolation was achieved before the loss of the SSC requiring circulating water cooling, and whether the core was damaged. In this embodiment, five flood damage states are included, ranked from most severe to least severe: FDS4, FDS3, FDS2, FDS1, and OK.

[0056] A flood consequence analysis is conducted for the flooded area, centered around the target pipeline. This analysis primarily involves determining the plant's flood spread path and mitigation information, calculating the maximum flooding level, assessing the impact of the flood on the plant's critical SSCs, and identifying the initiating events. This analysis focuses on the most severe flood consequences, including both direct and indirect impacts.

[0057] If the failed pipeline is the largest source of flooding in the flooded area (in fact, when analyzing the consequences of the failure of the pipeline, only the pipeline is considered as the only source of flooding), the consequence analysis of the flooded area can be directly applied; otherwise, further analysis is needed based on this basis and combined with the actual situation, such as screening "potentially failed" equipment based on test or operation data, project classification, and expert judgment; and reviewing the initiating event that caused it. If it is not in the previous analysis list, a new initiating event needs to be established.

[0058] Therefore, by using flooding scenario analysis and flooding consequence analysis, the direct and indirect impacts caused by pipeline failure are determined, and a basis is provided for subsequent quantitative analysis.

[0059] During the flooding analysis, the possibility of the operator isolating the pipeline was considered in the internal flooding PSA. In fact, the nuclear power plant pipeline failure consequence assessment method described in this embodiment also needs to consider the factor of pipeline rupture isolation.

[0060] The possibility of isolating a pipeline breach is also an important factor to be considered in the consequence analysis of pipeline failure. The breach can be isolated by protecting a check valve or closing an isolation valve, or it can be automatically isolated by closing the isolation valve through a specified signal; if there is no automatic isolation signal, it can be isolated by operator action. The possibility of isolating the breach depends on whether the isolation equipment is available, the method of detecting the breach, the available time to prevent specific consequences from occurring, and whether the operator's isolation action is successfully implemented. If the breach can be isolated, the consequences should be evaluated based on both successful and unsuccessful isolation. When isolation is successful, analyze the equipment affected by flooding under the condition of successful isolation and conduct a flooding consequence assessment; when isolation fails, analyze the equipment affected by flooding under the condition of failed isolation and conduct a flooding consequence assessment.

[0061] Therefore, in addition to the personnel actions modeled in PSA, the personnel actions of the isolation breach need to be modeled. The operator recovery action is considered credible only when the following conditions are met:

[0062] 1) There are alarms and / or clear instructions for the operator to respond;

[0063] 2) There are procedures to guide operator response;

[0064] 3) The equipment used for isolation (such as valves) is not affected by the breach;

[0065] 4) Sufficient time to implement quarantine and mitigate consequences.

[0066] Therefore, the relevant analysis conclusions of breach isolation in internal flooding PSA are applied to the pipeline failure consequence assessment of RI-ISI. The personnel actions are simulated and the corresponding values ​​are determined with reference to the existing internal flooding PSA model.

[0067] After completing the aforementioned qualitative analysis, a quantitative analysis of the consequences of target pipeline failure is conducted based on the results. The conditional probability of core damage and the conditional probability of early radioactive release are calculated to determine the consequence level of the target pipeline failure, completing the pipeline failure consequence assessment. Specifically, through qualitative analysis (i.e., flooding scenario analysis and flooding consequence analysis), the existing flooding PSA model is modified based on relevant initiating events and basic events to transform the qualitative analysis into a quantitative one.

[0068] The quantitative assessment methods for the consequences of pipeline failure are mainly divided into the following three situations:

[0069] 1) Pipeline failure-induced initiating event: In the PSA model, the corresponding initiating event frequency is set to 1, and the corresponding CCDP / CLERP is calculated. For example, if the qualitative analysis concludes that a pipeline failure caused a certain initiating event, in the quantitative assessment, the corresponding initiating event frequency in the PSA model is set to 1, and the corresponding CCDP / CLERP is calculated again. These two values ​​are used to determine the pipeline failure consequence level.

[0070] 2) Pipeline failure leads to mitigation system failure: The CCDP / CLERP calculation formula for this type of situation is:

[0071] CCDP=[CDF(F D )-CDF(Base)]·T t

[0072] CLERP=[LERF(F D )-LERF(Base)]·T t

[0073] Among them, CDF(F D ) / LERF(F D ) is the CDF / LERF under the failure condition of the specified system or series requirements, and the CDF(F D ) / LERF(F D) When it is necessary to set the series or components affected by the pipeline failure as failed in the PSA model, where the PSA model is obtained by modeling with the PSA professional software Risk Spectrum, and the PSA model specifically includes an event tree and a fault tree, and the above parameters are calculated based on this PSA model; similarly, CDF(Base) / LERF(Base) is calculated based on the PSA model, and CDF(Base) / LERF(Base) is the specific power plant benchmark CDF / LERF; T t is the failure exposure time. If the pipeline failure is immediately detected, the exposure time is equal to the allowed outage time (AOT) plus the time taken to detect the failure; if the pipeline failure is not detected in time, it is assumed that the exposure time is equal to the periodic test cycle, or if the equipment does not undergo periodic tests, the exposure time is equal to the whole year.

[0074] 3) The pipeline failure leads to an initiating event and the mitigation system fails: Set the corresponding initiating event frequency to 1 in the PSA model, and at the same time set the affected mitigation system and / or series as failed.

[0075] When quantitatively evaluating the consequences of pipeline failure, it is necessary to truly reflect the flooding scenario caused by the pipeline failure. If the flooding scenario has been modeled in the flooding PSA model, the CCDP / CLERP can be calculated by referring to its model settings. If there is no flooding scenario for reference, the model needs to be modified according to the previous qualitative analysis, such as establishing a new event tree or fault tree.

[0076] Determine the target pipeline failure consequence level based on the calculated conditional core damage probability CCDP and conditional early radioactive release probability CLERP, and complete the evaluation of the pipeline failure consequences.

[0077] As shown in Table 1 below, when CCDP > 1E-4 and CLERP > 1E-5, the target pipeline failure consequence is "high"; when 1E-6 < CCDP ≤ 1E-4 and 1E-7 < CLERP ≤ 1E-5, the target pipeline failure consequence is "medium"; when CCDP ≤ 1E-6 and CLERP ≤ 1E-7, the target pipeline failure consequence is "low".

[0078] Table 1 The ranges of CCDP and CLERP corresponding to the pipeline failure consequence levels

[0079] Consequence level Corresponding CCDP range Corresponding CLERP scope "high" CCDP>1E-4 CLERP>1E-5 "middle" 1E-6 <CCDP≤1E-4 1E-7 <CLERP≤1E-5 "Low" CCDP≤1E-6 CLERP≤1E-7

[0080] Among them, the definitions of each level are as follows:

[0081] 1) "High" consequence level: Trigger a pressure boundary failure, resulting in events that significantly contribute to the risk of the power plant and / or a serious deterioration of the power plant's mitigation capabilities;

[0082] 2) “Low” consequence level: 0 events that trigger pressure boundary failures, lead to expected operational events, and / or have no serious impact on the plant’s mitigation capabilities;

[0083] 3) “Medium” consequence level: failure of the pressure boundary between the “high” consequence level and the “low” consequence level;

[0084] 4) “None” consequence level: This type includes failures that have no impact on the risk, such as abandoned pipelines.

[0085] In summary, the nuclear power plant pipeline failure consequence assessment method described in this embodiment determines the flooding scenario caused by pipeline failure, including flooding spread and affected SSCs. The pipeline failure consequence assessment is completed through flooding area division, flooding scenario analysis, flooding consequence analysis, and breach isolation possibility analysis.

[0086] Example 2

[0087] This embodiment provides an electronic device, including a memory and a processor, and computer instructions stored in the memory and executed on the processor. When the computer instructions are executed by the processor, the steps of the nuclear power plant pipeline failure consequence assessment method based on internal flooding PSA are completed as described above.

[0088] Example 3

[0089] This embodiment further provides a computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, the steps in the nuclear power plant pipeline failure consequence assessment method based on internal flooding PSA are completed as described above.

[0090] The steps involved in the above embodiments 2 and 3 correspond to those in the method embodiment 1. For detailed implementation, please refer to the relevant description of embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media that includes one or more instruction sets; it should also be understood to include any medium that can store, encode, or carry an instruction set for execution by a processor and cause the processor to perform any method of the present invention.

[0091] Those skilled in the art will appreciate that the modules or steps of the present invention described above can be implemented using a general-purpose computer device. Alternatively, they can be implemented using program code executable by a computing device, which can then be stored in a storage device and executed by the computing device. Alternatively, they can be fabricated into separate integrated circuit modules, or multiple modules or steps can be fabricated into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0092] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

[0093] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A method for evaluating the consequences of nuclear power plant pipeline failure based on internal flooding PSA, characterized in that: include: Obtaining pipeline parameters of a target pipeline, where the target pipeline is any pipeline among the multiple pipelines to be evaluated; Taking the target pipeline as the flood source, determine the structures, systems or components affected by the flooding, as well as the flooding spread path; Conduct flooding scenario analysis and flooding consequence analysis to determine the direct and indirect impacts of target pipeline failure and achieve qualitative analysis of the consequences of target pipeline failure; Based on the results of the qualitative analysis, the consequences of target pipeline failure are quantitatively analyzed, the conditional probability of core damage and the conditional probability of early radioactive release are calculated, the level of the consequence of target pipeline failure is determined, and the pipeline failure consequence assessment is completed; Among them, through the qualitative analysis of flooding scenario analysis and flooding consequence analysis, based on the existing flooding PSA model, the relevant initiating events and basic events are modified to convert the qualitative analysis into quantitative analysis; Methods for quantitatively assessing the consequences of pipeline failure include: 1) Pipeline failure leading to an initiating event: In the PSA model, the corresponding initiating event frequency is set to 1, and the corresponding CCDP / CLERP is calculated, where CCDP is the conditional probability of core damage and CLERP is the conditional probability of early radioactive release. If the qualitative analysis concludes that a pipeline failure caused an initiating event, then in the quantitative assessment, the corresponding initiating event frequency in the PSA model is changed to 1, and the corresponding CCDP / CLERP is calculated again. The consequence level of the pipeline failure is determined based on these two values. 2) Pipeline failure leads to mitigation system failure: CCDP / CLERP calculation formula is: CCDP=[CDF(F D )-CDF(Base)]·T t ; CLERP=[LERF(F D )-LERF(Base)]·T t ; Among them, CDF(F D ) / LERF(F D ) is the CDF / LERF under the failure condition of the specified system or series requirements, and the CDF(F D ) / LERF(F D ), it is necessary to set the series or components affected by the pipeline failure as failure in the PSA model, wherein the PSA model is obtained by modeling using the PSA professional software Risk Spectrum. The PSA model specifically includes an event tree and a fault tree. The above parameters are calculated based on the PSA model; similarly, CDF(Base) / LERF(Base) is calculated based on the PSA model. CDF(Base) / LERF(Base) is the benchmark CDF / LERF for a specific power plant; T t is the fault exposure time. If the pipeline failure is discovered immediately, the exposure time is equal to the allowed outage time plus the time taken to discover the failure. If the pipeline failure is not discovered in time, the exposure time is assumed to be equal to the regular test period. If the equipment is not tested regularly, the exposure time is equal to the whole year. 3) Pipeline failure leads to initiating event and mitigation system failure: In the PSA model, the corresponding initiating event frequency is set to 1, and the affected mitigation system and / or series are set to fail.

2. The nuclear power plant pipeline failure consequence assessment method based on internal flooding PSA according to claim 1, characterized in that: Based on the spatial positions and equipment elevations of each structure, system and component determined in the internal flooding PSA qualitative analysis, as well as the possibility of each structure, system and component being affected by splashing, local flooding and major flooding and their corresponding mitigation facilities, the structures, systems and components affected by the target pipeline flooding are determined.

3. The nuclear power plant pipeline failure consequence assessment method based on internal flooding PSA according to claim 1, characterized in that: The structures, systems or components affected by the flooding include the equipment modeled in the internal flooding PSA model, that is, the equipment affected by the flooding and having an impact on the power plant risk; and also include the equipment not modeled in the internal flooding PSA model, that is, the equipment that is susceptible to flooding and whose failure will affect the normal operation of the power plant.

4. The method for evaluating the consequences of nuclear power plant pipeline failure based on internal flooding PSA according to claim 1, wherein: Based on the specific layout of the nuclear power plant and the flooding mitigation facilities, the flooding spread path after the target pipeline fails is determined.

5. The method for evaluating the consequences of nuclear power plant pipeline failure based on internal flooding PSA according to claim 1, wherein: The flooding scenario analysis specifically refers to establishing a flooding damage decision tree according to different failure conditions of the target pipeline and classifying different flooding damage states.

6. The method for evaluating the consequences of nuclear power plant pipeline failure based on internal flooding PSA according to claim 5, characterized in that: The process of establishing the flood damage decision tree is as follows: When the target pipeline fails, different flooding scenarios are first classified according to the target pipeline pressure boundary failure type, including: spraying, local flooding, and major flooding; Then, for different flooding scenarios, different flooding damage states are divided according to whether isolation is carried out before the loss of the circulating water system function, whether isolation is carried out before the loss of structures, systems or components requiring circulating water cooling, and whether the core is damaged.

7. The method for evaluating the consequences of nuclear power plant pipeline failure based on internal flooding PSA according to claim 1, wherein: The flood consequence analysis includes determining the flood spreading path and mitigation information of the power plant, calculating the maximum flooding water level, evaluating the impact of flooding on important structures, systems or components of the power plant, and identifying the initiating events that lead to flooding.

8. An electronic device, characterized in that: The invention comprises a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the steps of a nuclear power plant pipeline failure consequence assessment method based on internal flooding PSA according to any one of claims 1 to 7 are completed.

9. A computer-readable storage medium, characterized in that Used to store computer instructions, which, when executed by a processor, complete the steps of a nuclear power plant pipeline failure consequence assessment method based on internal flooding PSA according to any one of claims 1 to 7.

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