Method for regular safety evaluation and cumulative effect modification of nuclear power plant

Abstract

The invention relates to the technical field of nuclear power safety, in particular to a method for regular safety evaluation and cumulative effect modification of a nuclear power plant. A nuclear power plant regular safety evaluation and modification cumulative effect method comprises the following steps: obtaining implemented modification information, and establishing a nuclear power plant modification database; and establishing a function influence matrix, a determination theory safety analysis influence matrix, a probability theory safety analysis influence matrix, a disaster influence matrix, a radiation protection influence matrix, an external radiation environment influence matrix and an equipment identification influence matrix for each modification content in the nuclear power plant modification database. And obtaining a modified cumulative effect analysis evaluation result according to one or more types of analysis in the influence matrix. According to the method, the cumulative effects of all implemented modifications are systematically combed, the direct and indirect influence of the cumulative effects generated by all historical implemented modifications on the overall safety performance of the nuclear power plant is evaluated, and the reliability or effectiveness of the overall safety function of the nuclear power plant is maintained.

Description

Technical Field

[0001] This invention relates to the field of nuclear power safety technology, and in particular to a method for modifying the cumulative effects of periodic safety assessments of nuclear power plants. Background Technology

[0002] During the operational cycle of a nuclear power plant, numerous modifications to structures, systems, and equipment are required. While the safety of a single modification can be controlled through localized assessments, the cumulative effect of modifications across multiple systems, dimensions, and cycles can potentially impact the integrity of nuclear safety barriers, system functionality, and operational limits. To ensure the safe and stable operation of nuclear power plants, it is crucial to mitigate the adverse effects that may result from the cumulative effects of frequent modifications.

[0003] At the same time, nuclear power plant operators can incorporate the cumulative effects of modifications into their decennial periodic safety assessments, which require a systematic review of the cumulative effects of all implemented modifications and an assessment of their overall impact. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for modifying the cumulative effect of periodic safety assessments of nuclear power plants.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for modifying the cumulative effect of periodic safety assessments of nuclear power plants, comprising the following steps: Step S10: Obtain a list of safety functions based on the structures and nuclear island system of the nuclear power plant; Step S20: Obtain information on implemented modifications and establish a nuclear power plant modification database; Step S30: Conduct a safety function impact assessment for each modification in the nuclear power plant modification database and establish a function impact matrix; Step S40: Conduct a deterministic security analysis impact assessment for each of the modifications and establish a deterministic security analysis impact matrix; Step S50: Perform a probabilistic security analysis impact assessment on each of the modifications and establish a probabilistic security analysis impact matrix; Step S60: Conduct a disaster impact assessment for each of the modifications and establish a disaster impact matrix; Step S70: Conduct a radiation protection impact assessment for each of the modifications and establish a radiation protection impact matrix; Step S80: Perform an external radiation environmental impact analysis on each of the modifications and establish an external radiation environmental impact matrix; Step S90: Conduct an equipment appraisal impact assessment for each of the modifications and establish an equipment appraisal impact matrix; Step S100: Analyze and summarize one or more of the influence matrices from steps S30 to S90 to obtain the modified cumulative effect analysis and evaluation results.

[0006] Optionally, step S10 includes: The structure and the nuclear island system are analyzed to obtain the list of safety functions.

[0007] Optionally, step S20 includes: Obtain process data on the project initiation, technical analysis, implementation control, and safety evaluation of the modified projects to obtain the modified information. The modified information is integrated according to preset fields to obtain the nuclear power plant modification database.

[0008] Optionally, step S30 includes: Based on the safety function list and the nuclear power plant modification database, each modification is analyzed to obtain the safety functions involved in the modification; Based on the security functions involved in the modification, determine whether the security function list needs to be changed; if so, update the security function list to obtain the list of affected security functions. Based on the list of affected security functions, establish the function impact matrix.

[0009] Optionally, step S40 includes: Based on the list of deterministic safety analysis models for nuclear power plants and the nuclear power plant modification database, each modification is analyzed to obtain a list of affected deterministic safety analysis models involved in the modification. Based on the list of affected deterministic security analysis models, establish the deterministic security analysis impact matrix.

[0010] Optionally, step S50 includes: Based on the list of probabilistic safety analysis models for nuclear power plants and the nuclear power plant modification database, each modification is analyzed to obtain a list of probabilistic safety analysis models affected by the modification. Based on the list of affected probabilistic security analysis models, establish the probabilistic security analysis impact matrix.

[0011] Optionally, step S60 includes: Based on the nuclear power plant disaster assessment list and the nuclear power plant modification database, obtain a list of disaster mitigation measures involved in each modification; The risk mitigation capability of the disaster mitigation measures list is verified by using disaster scenario simulation; Based on the list of disaster mitigation measures and the risk mitigation capabilities, establish the disaster impact matrix.

[0012] Optionally, step S70 includes: The radiation protection impact assessment is conducted on each of the modifications based on the functions of the nuclear power plant's structures, systems, and equipment, and the radiation protection impact matrix is ​​established.

[0013] Optionally, step S80 includes: The impact of each modification on the external radiation environment of the nuclear power plant under normal and accident operating conditions is obtained, and the external radiation environment impact matrix is ​​established.

[0014] Optionally, step S90 includes: Obtain the qualification test of the equipment involved in each of the modifications; Based on each of the aforementioned modifications, an impact matrix for device identification is established.

[0015] Optionally, step S100 includes: Based on the aforementioned "Functional Impact Matrix", security functions affected by two or more modifications are selected; based on the aforementioned "Functional Impact Matrix", the cumulative effect of the modifications on the security functions is evaluated; Based on the aforementioned "deterministic security analysis impact matrix", deterministic security analysis models affected by two or more modifications are selected, and the cumulative effect of modifications on the deterministic security analysis results is calculated. Based on the cumulative effect of modifications on the deterministic security analysis results, the cumulative effect of modifications on the deterministic security analysis models is evaluated. Based on the aforementioned "probabilistic security analysis impact matrix", probabilistic security analysis models affected by two or more modifications are selected, and the cumulative probabilistic security analysis results after modification are calculated; the cumulative effect of modification on the probabilistic security analysis models is evaluated based on the cumulative probabilistic security analysis results after modification. Based on the "Disaster Impact Matrix", select internal and external disaster mitigation measures that are affected by two or more modifications; evaluate the cumulative effect of the modifications to the internal and external disaster mitigation measures based on the "Disaster Impact Matrix". Radiation protection measures affected by two or more modifications are selected based on the radiation protection impact matrix; the cumulative effect of the modifications to the radiation protection measures is evaluated based on the radiation protection impact matrix. Based on the aforementioned "external radiation environment impact matrix", external radiation environment impact indicators and protection measures affected by two or more modifications are selected; based on the external radiation environment impact indicators and protection measures, the cumulative effect of the modifications to the external radiation environment is evaluated; Based on the device identification impact matrix, device identifications affected by two or more modifications are selected; based on the device identification impact matrix, the cumulative effect of the modifications on the device identification is evaluated; The cumulative effects of modifications to the safety functions, deterministic safety analysis model, probabilistic safety analysis model, measures to resist internal and external disasters, radiation protection measures, external radiation environment, and equipment identification are summarized to obtain risk points, a list of problems, and rectification suggestions as the results of the cumulative effect analysis.

[0016] The implementation of this invention has the following beneficial effects: This invention establishes one or more of the following matrices based on each modification: functional impact matrix, deterministic safety analysis impact matrix, probabilistic safety analysis impact matrix, disaster impact matrix, radiation protection impact matrix, external radiation environment impact matrix, and equipment qualification impact matrix. This quantifies safety risks in different dimensions, systematically reviews the cumulative effects of all implemented modifications, and assesses the direct and indirect impacts of each modification and the cumulative effects of implemented modification information on the overall safety performance of the nuclear power plant, thereby maintaining the reliability or effectiveness of the overall safety functions of the nuclear power plant. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a flowchart of a method for modifying the cumulative effects of periodic safety assessments of nuclear power plants, as illustrated in one embodiment. Detailed Implementation

[0018] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0020] This invention provides a method for modifying the cumulative effects of periodic safety assessments of nuclear power plants, such as... Figure 1 As shown, it includes the following steps: Step S10: Obtain a list of safety functions based on the structures and nuclear island system of the nuclear power plant.

[0021] After obtaining the list of safety functions, a detailed analysis and evaluation of each function is conducted. This includes determining the importance of each safety function in the operation of the nuclear power plant, classifying it into different importance levels based on its role in ensuring nuclear safety, preventing nuclear accidents, and mitigating the consequences of accidents. Simultaneously, for each safety function, the related equipment, components, and systems are identified, clarifying their interrelationships and mutual influences, so that the cumulative effects of periodic safety assessment modifications can be comprehensively and accurately analyzed subsequently.

[0022] Step S20: Obtain implemented modification information and establish a nuclear power plant modification database.

[0023] Based on the implemented modifications, a database system that is "complete in information, closely linked, with controllable permissions, and traceable" will be constructed to achieve full-process data integration from modification project initiation, technical analysis, implementation control to safety evaluation. This will provide accurate data support for safety impact assessment, risk management and regulatory reporting, and ensure the compliance and safety of nuclear power plant modification projects.

[0024] Step S30: Conduct a safety function impact assessment for each modification in the nuclear power plant modification database and establish a function impact matrix.

[0025] Determine whether the security function list needs to be changed based on the security functions involved in the modification; if so, update the security function list. Establish a "Function Impact Matrix" based on the list of affected security functions.

[0026] Based on the aforementioned "Functional Impact Matrix", security functions affected by two or more modifications are selected. The cumulative effect of the modifications to the security functions is assessed based on the aforementioned "functional impact matrix".

[0027] Step S40 involves conducting a deterministic security analysis impact assessment for each of the modifications and establishing a deterministic security analysis impact matrix. For each modification, determine whether the parameters of the security analysis model have been changed; if so, calculate whether the change has a security impact. If so, compare the deterministic analysis results before and after the parameter modification; determine whether the deterministic analysis results meet the safety limit requirements. Based on the list of affected deterministic security analysis models, a "deterministic security analysis impact matrix" is established.

[0028] Based on the "deterministic security analysis influence matrix", deterministic security analysis models affected by two or more modifications are selected, and the cumulative deterministic security analysis results after modification are calculated. Based on the cumulative results of the deterministic security analysis, the cumulative effect of the modifications on the deterministic security analysis model is evaluated.

[0029] Step S50: Perform a probabilistic security analysis impact assessment on each of the modifications and establish a probabilistic security analysis impact matrix; For each modification, determine whether the parameters of the probabilistic security analysis model have been changed; if so, calculate whether the change has a security impact. If so, compare the probability analysis results before and after the parameter modification; determine whether the probability analysis results meet the safety limit requirements. Based on the list of affected probability theory security analysis models, a "probabilistic security analysis impact matrix" is established.

[0030] Based on the "probabilistic security analysis impact matrix", probabilistic security analysis models affected by two or more modifications are selected, and the probabilistic security analysis results after the cumulative modification are calculated. Based on the cumulative results of the modified probabilistic security analysis, the cumulative effect of the modification on the probabilistic security analysis model is evaluated.

[0031] Step S60: Conduct a disaster impact assessment for each modification and establish a "disaster impact matrix".

[0032] The disaster mitigation impact assessment focuses on how each modification performs under extreme natural disasters or accident conditions, evaluating its resilience and potential impacts. The radiation protection impact assessment focuses on whether modifications will impact the nuclear power plant's radiation protection system, ensuring the radiation safety of workers and the public.

[0033] Step S70: Conduct a radiation protection impact assessment for each modification and establish a "radiation protection impact matrix".

[0034] The external radiation environmental impact assessment comprehensively examines the potential impact of each modification on the surrounding environment, including but not limited to the release of liquid effluents, gaseous effluents, solid radioactive waste, and the maintenance of ecological balance. By synthesizing the results of one or more of the above analyses, a cumulative effect analysis and evaluation of the modifications is derived, assessing their overall impact and providing strong assurance for the continued safe operation of the nuclear power plant.

[0035] Step S80: Conduct an external radiation environmental impact assessment for each modification and establish an "external radiation environmental impact matrix".

[0036] The results of external radiation environmental impact assessments not only visually reflect the specific numerical impact of each modification on the surrounding radiation environment, but also further analyze the changing trends of this impact in time and space. For liquid effluents, the assessment results will clearly identify the types, concentrations, and total emissions of radioactive materials, and analyze their potential hazards to the surrounding aquatic ecosystems. For gaseous effluents, the assessment will focus on the diffusion range and deposition of radioactive gases, considering the impact of meteorological conditions such as wind direction, wind speed, and atmospheric stability on their diffusion. For solid radioactive waste, the assessment will evaluate whether its treatment and storage methods are safe and reliable, whether there is a risk of radioactive material leakage, and the potential pollution of surrounding soil and groundwater. Through a comprehensive analysis and assessment of these external radiation environmental factors, it is ensured that the nuclear power plant achieves safe operation while minimizing its adverse impacts on the surrounding environment.

[0037] Step S90: Conduct an equipment appraisal impact assessment for each modification and establish an "equipment appraisal impact matrix".

[0038] The assessment results will detail the impact of modifications on the equipment qualification benchmark tests, tests under extreme operating conditions, tests on equipment performance over time (thermal aging tests, accelerated damp heat tests, long-term operation tests, mechanical vibration tests, and cumulative radiation tests during operation), tests under accident and post-accident conditions (seismic load tests, seismic calculations, cumulative radiation tests during accidents, and Loss of Coolant Accident (LOCA) tests), and electromagnetic compatibility tests.

[0039] Based on these detailed assessments, the results will be further compared with the requirements in the equipment qualification outline. This will check whether the assessment results meet the various safety standards and performance requirements stipulated in the equipment qualification outline. If there are discrepancies between the assessment results and the list requirements, the reasons for the discrepancies will be analyzed in depth to determine whether the modifications themselves are unreasonable or whether there are potential problems with the equipment itself.

[0040] Step S100: Analyze and summarize one or more of the influence matrices from steps S30 to S90 to obtain the modified cumulative effect analysis and evaluation results.

[0041] It is understandable that one or more of the influence matrices in steps S30 to S90 refer to one or more of the following: functional influence matrix, deterministic safety analysis influence matrix, probabilistic safety analysis influence matrix, disaster influence matrix, radiation protection influence matrix, external radiation environment influence matrix, and equipment qualification influence matrix.

[0042] This invention establishes one or more of the following impact matrices for each modification: functional impact matrix, deterministic safety analysis impact matrix, probabilistic safety analysis impact matrix, disaster impact matrix, radiation protection impact matrix, external radiation environment impact matrix, and equipment qualification impact matrix. This allows for analysis of each modification through one or more of the following methods: safety function impact assessment, deterministic safety analysis impact assessment, probabilistic safety analysis impact assessment, disaster mitigation impact assessment, radiation protection impact assessment, external radiation environment impact assessment, and equipment qualification impact assessment. Furthermore, it systematically reviews the cumulative effects of all implemented modifications, assessing their direct and indirect impacts on the overall safety performance of the nuclear power plant, and determining whether they reduce the reliability or effectiveness of existing safety functions.

[0043] In one embodiment, step S10 includes: An analysis of the structures and nuclear island system yielded a nuclear power functional list.

[0044] The study examines all structures and systems in a nuclear power plant, covering the nuclear island, conventional island, auxiliary systems, and utilities. It comprehensively identifies all structures (such as reactor buildings, turbine buildings, emergency diesel generator buildings, and radioactive waste treatment buildings) and systems (such as primary loop systems, secondary loop systems, safety injection systems, equipment cooling water systems, and instrumentation and control systems).

[0045] Based on the aforementioned list of nuclear power plant structures and systems, the core and auxiliary functions of each structure and system are analyzed one by one to clarify the functions and compile a nuclear power function list for the nuclear power plant.

[0046] The list of nuclear power functions is obtained by screening the list of nuclear power functions based on safety limit standards.

[0047] Based on nuclear safety regulations (such as HAF102 "Safety Regulations for Nuclear Power Plant Design"), the Final Safety Analysis Report (FSAR) of nuclear power plants, and industry standards, safety functions are selected from the nuclear power functional list to obtain the safety functional list.

[0048] Based on nuclear safety regulations (such as HAF102 "Safety Regulations for Nuclear Power Plant Design"), the Final Safety Analysis Report (FSAR) of nuclear power plants, and industry standards, screening safety functions from the nuclear power plant functional list can effectively identify functional items that are crucial to the safe operation of nuclear power plants. These functional items not only cover core safety objectives such as directly ensuring the safe shutdown of nuclear reactors and preventing the release of radioactive materials, but also include key auxiliary functions that can mitigate the consequences of accidents and maintain the controllable state of the power plant under accident conditions, ensuring the comprehensiveness and accuracy of the safety functional list.

[0049] Furthermore, security features include: 1) Functions that directly affect nuclear safety; 2) The functions provided in the Final Safety Analysis (FSAR) report for nuclear power plants for mitigating transient, design basis, and selected beyond design basis accidents; 3) Functions required to execute accident procedures (design basis accidents); 4) Non-safety functions that directly affect safety functions after failure.

[0050] The selected security functions are uniformly coded to form a security function list.

[0051] In one embodiment, step S20 includes: Obtain process data on the project initiation, technical analysis, implementation control, and safety evaluation of implemented modification projects to obtain information on implemented modifications.

[0052] Acquire and organize process data from all stages of implemented modification projects, including project initiation, technical analysis, implementation control, and safety evaluation, to comprehensively collect and summarize relevant information on implemented modifications.

[0053] The modified information is integrated according to the preset fields to obtain the nuclear power plant modification database.

[0054] Each modified document is reviewed, with a focus on verifying its completeness (e.g., whether all involved SSCs and interfaces are clearly identified), accuracy (e.g., whether design parameter changes are clear and technical solutions are feasible), and compliance (e.g., whether it complies with nuclear safety regulations). The implemented modification information is then integrated and summarized based on completeness, accuracy, and compliance to create a nuclear power plant modification database.

[0055] In one embodiment, step S30 includes: Each modification is analyzed based on the safety function list and the nuclear power plant modification database to obtain the associated safety functions.

[0056] Understandably, the database for nuclear power plant modifications is used to comprehensively identify all interfaces involved in each modification, including mechanical interfaces (such as pipe connections and equipment flange connections), electrical interfaces (such as cable connections and electrical circuit associations), instrumentation and control interfaces (such as signal transmission and control logic associations), and auxiliary system interfaces (such as gas supply interfaces, cooling water interfaces, and steam interfaces).

[0057] For each interface, identify the system / equipment to which it belongs (e.g., cooling water interface belongs to equipment cooling water system, signal interface belongs to nuclear testing and control system), compare with the safety function list, analyze the function to which the above interface belongs, and obtain the associated functions to be modified.

[0058] Determine whether the security function list needs to be changed based on the security functions involved in the modification; if so, update the security function list to obtain the list of affected security functions.

[0059] Furthermore, by querying the associated devices based on the security functions involved in the modification, a list of devices to be explored can be obtained.

[0060] The modification association function can be used to query and obtain all relevant modified association equipment information, thereby generating a list of equipment to be explored.

[0061] The equipment was explored according to the list of equipment to be explored, and the exploration results were obtained.

[0062] The exploration content includes the current operating status of the equipment, the integrity of the physical structure, and changes in performance parameters. It also records in detail all data and information obtained during the exploration process, ultimately forming an accurate and complete exploration result.

[0063] The exploration results were analyzed to obtain a list of affected functions.

[0064] Specifically, the analysis of exploration results includes: 1) Spatial interference: The spatial relationship between each modified SSC and its surrounding SSCs, whether there are installation conflicts or insufficient operation and maintenance space (such as valve handles being blocked by newly added equipment, making emergency operation impossible); specifically, SSC refers to the structure, system and equipment functions of a nuclear power plant.

[0065] 2) Functional interference: Does each modification affect the normal operation of surrounding SSCs (e.g., does the vibration of the newly added equipment cause measurement deviations of nearby instruments, or does the newly added cable interfere with the original signal transmission)? 3) Safety distance: After each modification, does the distance between the SSC and radiation sources, high-temperature equipment, and high-pressure pipelines meet safety requirements, and does it affect the "radiation shielding function" and "fire and explosion prevention function"?

[0066] 4) Earthquake-induced interference: The spatial relationship between each modified SSC and its surrounding SSCs, and whether it will endanger safety-related equipment under earthquake conditions.

[0067] Based on the on-site photos from the above four aspects, record the measurement data, clarify whether the interference affects the safety function, and thus obtain the affected function.

[0068] Update the security features list based on the affected features, and obtain the list of affected security features.

[0069] Summarize all security features affected by each modification to determine if any security features have been removed or added. If any features have been removed or added, revise the security feature list.

[0070] Based on the list of affected security features, create a feature impact matrix.

[0071] In Periodic Safety Reviews (PSRs), all modifications for which functional impact assessments have been completed are summarized to create a functional impact matrix. The horizontal axis of the functional impact matrix represents each modification, and the vertical axis represents safety functions. In some scenarios, the functional impact matrix is ​​presented in tabular form (see Table 1) to qualitatively confirm whether there is an impact.

[0072] Table 1 In one embodiment, step S40 includes: Based on the list of deterministic safety analysis models for nuclear power plants and the nuclear power plant modification database, each modification is analyzed to obtain a list of affected deterministic safety analysis models involved in the modification.

[0073] Specifically, based on the modified database of the nuclear power plant, the modification parameters for each modified item in the deterministic safety analysis model are obtained.

[0074] Identify the deterministic safety analysis model in the Final Safety Analysis Report (FSAR) affected by this modification, such as all accident analysis models covered by the FSAR. Assess whether each modification alters the model's input parameters (e.g., equipment rated capacity, system flow coefficient, pipeline resistance characteristics), boundary conditions (e.g., pressure boundaries, temperature limits, initial operating conditions), or analytical assumptions (e.g., accident triggering conditions, equipment failure criteria). If input parameters and analytical assumptions are affected, a "parameter sensitivity analysis" should be conducted to analyze the degree of impact on the accident analysis results before and after the revision, determining whether the modification causes the model calculation results to exceed safety limits (e.g., whether the maximum core temperature exceeds the limit). Prepare a report on the impact of the modification on the deterministic safety analysis, clearly stating the impact conclusions (no impact / model update required) and the basis for judgment.

[0075] Based on the list of affected deterministic security analysis models, a deterministic security analysis impact matrix is ​​established.

[0076] The Periodic Security Review (PSR) summarizes all modifications for which deterministic security analysis model impact assessments have been completed, and establishes a deterministic security analysis impact matrix. The x-axis of the deterministic security analysis impact matrix represents each modification, and the y-axis represents the deterministic security analysis model. In some scenarios, the deterministic security analysis impact matrix is ​​presented in tabular form (see Table 2) to qualitatively confirm whether there is an impact.

[0077] Table 2 Based on each modification, determine whether the parameters of the deterministic security analysis model have been changed; if so, determine whether the change has a security impact. If so, compare the deterministic analysis results before and after the parameter changes in the deterministic security analysis model; determine whether the deterministic analysis results meet the security limit requirements.

[0078] Specifically, if the modification is deemed to have an impact on the model, the deterministic safety analysis professionals will carry out the model update work, recalculate using professional analysis software, compare the key results before and after the model update, and verify whether the updated model meets the acceptance criteria and nuclear safety regulations.

[0079] In one embodiment, step S50 includes: Based on the list of probabilistic safety analysis models for nuclear power plants and the nuclear power plant modification database, each modification is analyzed to obtain the probabilistic safety analysis model involved in the modification.

[0080] Based on the list of affected probability theory security analysis models, a probability theory security analysis impact matrix is ​​established.

[0081] The Periodic Security Review (PSR) summarizes all modifications for which probabilistic security analysis model impact assessments have been completed, and establishes a probabilistic security analysis impact matrix. The x-axis of the probabilistic security analysis impact matrix represents each modification, and the y-axis represents the probabilistic security analysis model. In some scenarios, the probabilistic security analysis impact matrix is ​​presented in tabular form (see Table 3) to qualitatively confirm whether there is an impact.

[0082] Table 3 Understandably, for each modification, it is determined whether the parameters of the probabilistic security analysis model have been changed; if so, it is determined whether the change has a security impact.

[0083] If so, compare the probabilistic analysis results before and after the parameter changes in the probabilistic security analysis model; determine whether the probabilistic analysis results meet the security limit requirements.

[0084] In some scenarios, the PSA model elements involved in each modification are identified based on the safety function list and nuclear power plant modification database. These elements include equipment reliability parameters (such as failure rate, maintenance time, and availability), system availability logic (such as gate structure and minimum cut set of fault tree), incident sequences (such as triggering events and mitigation nodes of event tree), and risk indicator calculation parameters (such as consequence factors).

[0085] To determine whether each modification alters these elements, a "risk contribution analysis" is used to assess the magnitude of the impact. It is determined whether the modification leads to significant changes in core risk indicators (such as core damage frequency (CDF) and large radioactive release frequency (LERF)). The conclusion of the impact (no impact / model needs to be updated) and the degree of impact are then clarified.

[0086] If it exists, compare the results before and after the change of elements in the probabilistic security analysis model.

[0087] If it is determined that each modification affects the PSA model, PSA professionals will update the model, adjust reliability parameters, optimize the logical structure, recalculate risk indicators, and conduct a new quantitative analysis using PSA analysis software to calculate the updated CDF, LERF, and importance indicators.

[0088] In one embodiment, step S60 includes: Based on the nuclear power plant disaster assessment list and the nuclear power plant modification database, obtain a list of disaster mitigation measures involved in each modification.

[0089] By simulating disaster scenarios, the risk mitigation capabilities of the disaster mitigation measures list are verified.

[0090] The revised design of systems and equipment, along with surrounding equipment, is reviewed and compared with a list of internal disaster mitigation measures and external disaster mitigation facilities at the nuclear power plant. The impact of the modifications on the plant's ability to withstand internal disasters (such as fire, flooding, explosions, and pipeline ruptures) and external disasters (such as earthquakes, floods, typhoons, and extreme temperatures) is analyzed. A "disaster scenario simulation + capability verification" approach is used to determine whether the modifications weaken disaster mitigation capabilities, clarifying the impact conclusions and improvement measures.

[0091] The revised design of the systems and equipment, along with their surrounding equipment, was reviewed and compared with a list of nuclear power plant's internal disaster mitigation measures and external disaster mitigation facilities.

[0092] Establish a disaster impact matrix based on the list of disaster mitigation measures and risk mitigation capabilities.

[0093] The Periodic Safety Assessment (PSR) compiles all modifications that have completed disaster resilience impact assessments, creating a disaster impact matrix. The horizontal axis of the disaster impact matrix represents each modification, and the vertical axis represents the mitigation measures for internal and external disasters. In some scenarios, the disaster impact matrix is ​​presented in tabular form (see Table 4) to qualitatively confirm whether there is an impact.

[0094] Table 4 In one embodiment, step S70 includes: The radiation protection impact assessment is conducted on each of the modifications based on the functions of the nuclear power plant's structures, systems, and equipment, and the radiation protection impact matrix is ​​established.

[0095] It should be noted that the functions of nuclear power plant structures, systems, and equipment are also referred to as SSC functions. This analysis, considering the modified functions of nuclear power plant structures, systems, and equipment (such as radioactive equipment, radiation sources, shielding facilities, radiation zoning, and the radioactive containment and filtration of ventilation systems), examines aspects such as radiation sources, radiation shielding, radiation monitoring, and personal protective equipment. Based on relevant regulations and standards for nuclear power plant radiation protection, the impact conclusions are clarified.

[0096] The Periodic Safety Assessment (PSR) compiles all modifications for which radiation protection impact assessments have been completed, creating a radiation protection impact matrix. The horizontal axis of the matrix represents each modification, and the vertical axis represents the radiation protection measures implemented. In some scenarios, the radiation protection impact matrix is ​​presented in tabular form (see Table 5) to qualitatively confirm whether there is an impact.

[0097] Table 5 In one embodiment, step S80 includes: Obtain the impact of each modification on the external radiation environment of the nuclear power plant under normal and accident operating conditions, and establish an external radiation environment impact matrix.

[0098] Specifically, analyze the radiation impact of the modifications on the external environment (air, water, soil, and organisms) of the nuclear power plant, including normal and accident operating conditions. Use external radiation environmental impact assessment methods (such as model calculations and analog analysis) to predict the degree of external radiation environmental impact after the modifications. If major changes are involved, supplementary external radiation environmental impact assessments must be carried out in accordance with regulations. Clarify the radiation impact conclusions and environmental protection measures (such as adding advanced wastewater treatment units and optimizing exhaust gas emission paths).

[0099] The Periodic Safety Assessment (PSR) compiles all modifications to completed external radiation environmental impact assessments of nuclear power plants, establishing an external radiation environmental impact matrix. The horizontal axis of the matrix represents each modification, and the vertical axis represents external radiation environmental monitoring and protection measures. In some scenarios, the external radiation environmental impact matrix is ​​presented in tabular form (see Table 6) to qualitatively confirm whether an impact has occurred.

[0100] Table 6 In one executable embodiment, step S90 includes: Obtain the qualification tests for the equipment involved in each modification.

[0101] The analysis examines the impact of modifications on nuclear power plant equipment qualification, including the modification of benchmark tests, tests under extreme operating conditions, tests on equipment performance over time (thermal aging tests, accelerated damp heat tests, long-term operation tests, mechanical vibration tests, and cumulative irradiation tests), tests under accident and post-accident conditions (seismic load tests, seismic calculations, accident cumulative irradiation tests, and coolant loss accident LOCA tests), and electromagnetic compatibility tests. The analysis clarifies the conclusions regarding the impact on equipment qualification.

[0102] Based on each of the aforementioned modifications, an equipment identification impact matrix is ​​established for the identification test.

[0103] Specifically, a Equipment Qualification Impact Matrix can be created by summarizing all modifications that have completed equipment qualification impact assessments in the Periodic Safety Review (PSR). The horizontal axis represents each modification, and the vertical axis represents the equipment to be qualified. In some scenarios, the Equipment Qualification Impact Matrix is ​​presented in tabular form (see Table 7) to qualitatively confirm whether there is an impact.

[0104] Table 7 In one embodiment, step S100 includes: Security functions affected by two or more modifications are identified based on the functional impact matrix; the cumulative effect of these modifications on security functions is then assessed based on the functional impact matrix.

[0105] Specifically, from the functional impact matrix, identify the same safety function affected by two or more modifications. Organize expert reviews (including safety impact assessment, system design, and equipment maintenance professionals) to analyze the cumulative impact of multiple modifications on the function. If a weakening effect exists, assess whether the cumulative effect will cause the function to fail to meet safety requirements (e.g., whether emergency power supply reliability drops below the threshold). If the impact type is complex (partial enhancement, partial weakening), the final performance indicators of the function need to be quantitatively calculated. Obtain the cumulative effect of the modifications in the safety impact assessment based on the final performance indicators.

[0106] Furthermore, different quantification methods are adopted based on different functions. For example, if it affects the core cooling function, the cladding temperature of the fuel assembly needs to be modeled and calculated; if it affects the stress of the pipeline, a mechanical calculation model of the pipeline is established for quantification.

[0107] Based on the deterministic security analysis influence matrix, deterministic security analysis models affected by two or more modifications are selected, and the cumulative deterministic security analysis results after modification are calculated; the cumulative effect of modification on the deterministic security analysis models is evaluated based on the cumulative deterministic security analysis results after modification.

[0108] Specifically, we screen out deterministic safety analysis models affected by two or more modifications. We assess the cumulative impact of multiple modifications on the model, analyze the superposition effect of parameter changes and the combined effect of boundary condition adjustments, and determine whether the model can still accurately reflect the actual safety status of nuclear power plants.

[0109] Select a deterministic security analysis model to be confirmed from the deterministic security analysis models that meet the security limit requirements and are subject to at least two security influences.

[0110] The changes in the modified parameters of the deterministic security analysis model to be confirmed are analyzed to obtain the cumulative impact of the modifications.

[0111] Based on the cumulative effects of the modifications, the cumulative effect of modifications on the deterministic security analysis is obtained.

[0112] Based on the probabilistic security analysis influence matrix, probabilistic security analysis models affected by two or more modifications are selected, and the cumulative probabilistic security analysis results after modification are calculated; the cumulative effect of modification on the probabilistic security analysis models is evaluated based on the cumulative probabilistic security analysis results after modification.

[0113] Identify elements of the same PSA (Probabilistic Safety Analysis) model that are affected by two or more modifications. Assess the cumulative effect of multiple modifications: if multiple modifications reduce equipment failure rates, verify whether the risk indicators are excessively reduced (resource allocation can be optimized); if some modifications increase risk while others reduce it, quantify the net risk change; if multiple modifications significantly increase the risk contribution of a minimum cut set, identify it as a new vulnerability. Determine the evaluation conclusion (risk acceptable / risk control required); if risk control is required, develop measures (such as increasing equipment redundancy, optimizing maintenance plans), and track the implementation of these measures to ensure the risk level remains within acceptable limits.

[0114] Based on the disaster impact matrix, select measures to mitigate internal and external disasters that are affected by two or more modifications; assess the cumulative effect of modifications to these measures based on the disaster impact matrix.

[0115] The disaster resilience of nuclear power plants is quantitatively assessed based on each modification and its corresponding internal and external disaster mitigation measures. Specifically, a series of assessment indicators, such as the effectiveness of mitigation measures and the degree to which the modifications enhance or weaken the original resilience, can be used to score or rate each modification. Summarizing and analyzing these assessment results provides a clear understanding of the impact of the modifications on the overall disaster resilience of the nuclear power plant. Furthermore, targeted improvement measures can be proposed based on the assessment results to further enhance the safety performance of the nuclear power plant.

[0116] Furthermore, by assessing the cumulative effect of multiple modifications, if there is an impact that weakens the measures to resist internal and external disasters, it is assessed whether the cumulative effect will lead to the measures to resist internal and external disasters failing to meet the design requirements; if the impact is complex (partial enhancement, partial weakening), a calculation model needs to be established based on the relevant standards for nuclear power plant disaster design to quantify the final performance indicators of the measures to resist internal and external disasters.

[0117] Radiation protection measures affected by two or more modifications are screened based on the radiation protection impact matrix; the cumulative effect of modifications to radiation protection measures is evaluated based on the radiation protection impact matrix.

[0118] A thorough evaluation will be conducted on radiation protection measures identified as being affected by two or more modifications, analyzing the interactions and cumulative effects among these modifications. The temporal, spatial, and functional relationships between different modifications will be considered to determine whether they will produce synergistic or conflicting effects. For example, some modifications may have a positive impact on radiation protection measures when implemented individually, but when multiple modifications are implemented simultaneously, unexpected negative effects may occur.

[0119] Assess the cumulative effect of multiple modifications. If there is an impact that weakens radiation protection measures, assess whether the cumulative effect will cause the radiation protection measures to fail to meet design requirements. If the impact is complex (partial enhancement, partial weakening), a calculation model should be established based on the relevant standards for radiation protection design of nuclear power plants to quantify the final performance indicators of radiation protection measures.

[0120] Based on the external radiation environment impact matrix, external radiation environment impact indicators and protection measures affected by two or more modifications are screened out; based on the external radiation environment impact indicators and protection measures, the cumulative effect of modifications to the external radiation environment is assessed.

[0121] External radiation environmental impact indicators and protection measures affected by two or more modifications require focused attention and in-depth analysis. For the selected indicators and measures, a professional radiation protection and environmental monitoring team should be organized to assess the comprehensive impact of the combined effects of multiple modifications on these indicators and measures using advanced monitoring equipment and scientific analysis methods.

[0122] Assess the cumulative effect of multiple modifications. If there is an impact that weakens the environmental impact indicators and protection measures of external radiation of nuclear power plants, assess whether the cumulative effect will lead to the failure of the environmental impact indicators and protection measures of external radiation of nuclear power plants to meet the design requirements. If the impact type is complex (partial enhancement, partial weakening), a calculation model needs to be established based on the relevant standards for radiation environmental protection of nuclear power plants to quantify the final performance indicators of the environmental impact indicators and protection measures of external radiation of nuclear power plants.

[0123] Equipment identification affected by two or more modifications is screened based on the equipment identification impact matrix; the cumulative effect of modifications on equipment identification is assessed based on the equipment identification impact matrix.

[0124] Equipment qualification affected by two or more modifications is part of the nuclear power plant equipment safety assessment, requiring further in-depth analysis of the complex impacts that may arise from the superposition of multiple modifications. First, the nature and extent of each relevant modification must be thoroughly analyzed to determine whether there are any synergistic effects on equipment qualification parameters and environmental conditions. For these identified affected equipment qualification parameters and environmental conditions, an interdisciplinary expert team should be organized to conduct an assessment. Team members should cover multiple fields such as nuclear physics, mechanical engineering, and electrical systems to ensure a comprehensive consideration of all aspects of the equipment. Experts can then use their professional knowledge and past experience to predict and assess the equipment qualification under the influence of multiple modifications.

[0125] By assessing the cumulative effect of multiple modifications, if there is an impact that weakens the equipment qualification parameters or environmental conditions, assess whether the cumulative effect will cause the equipment qualification to fail to meet the design requirements; if the impact type is complex (partial enhancement, partial weakening), qualification tests should be carried out according to the relevant equipment qualification standards, and the comprehensive impact of the equipment qualification should be evaluated through the tests.

[0126] The cumulative effects of modifications to safety functions, deterministic safety analysis models, probabilistic safety analysis models, measures to resist internal and external disasters, radiation protection measures, external radiation environment, and equipment appraisal are summarized to obtain risk points, a list of problems, and rectification suggestions as the results of the cumulative effect analysis and evaluation.

[0127] Among them, the cumulative effect of modifications to safety functions is the assessment result of the safety function impact assessment; the cumulative effect of modifications to the deterministic safety analysis model is the assessment result of the deterministic safety analysis impact assessment; the cumulative effect of modifications to the probabilistic safety analysis model is the assessment result of the probabilistic safety analysis impact assessment; the cumulative effect of modifications to measures to resist internal and external disasters is the assessment result of the disaster measures impact assessment; the cumulative effect of modifications to radiation protection measures is the assessment result of the radiation protection impact assessment; the cumulative effect of modifications to the external radiation environment is the assessment result of the external radiation environment impact assessment; and the cumulative effect of modifications to equipment appraisal is the assessment result of the equipment appraisal impact assessment.

[0128] Understandably, Periodic Safety Assessments (PSRs) summarize the impact assessments of safety functions, deterministic safety analysis, probabilistic safety analysis, disaster mitigation measures, radiation protection, and external radiation environment. They clarify overall safety conclusions (e.g., cumulative impacts are within acceptable limits / there are risks requiring close monitoring), a list of specific issues (e.g., performance degradation of a safety function due to multiple modifications), and rectification recommendations. This summary can be done using tables, databases, or computer software.

[0129] The above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for modifying the cumulative effect of periodic safety assessments of nuclear power plants, characterized in that, Includes the following steps: Step S10: Obtain a list of safety functions based on the structures and nuclear island system of the nuclear power plant; Step S20: Obtain information on implemented modifications and establish a nuclear power plant modification database; Step S30: Conduct a safety function impact assessment for each modification in the nuclear power plant modification database and establish a function impact matrix; Step S40: Conduct a deterministic security analysis impact assessment for each of the modifications and establish a deterministic security analysis impact matrix; Step S50: Perform a probabilistic security analysis impact assessment on each of the modifications and establish a probabilistic security analysis impact matrix; Step S60: Conduct a disaster impact assessment for each of the modifications and establish a disaster impact matrix; Step S70: Conduct a radiation protection impact assessment for each of the modifications and establish a radiation protection impact matrix; Step S80: Conduct an external radiation environmental impact assessment for each of the modifications and establish an external radiation environmental impact matrix; Step S90: Conduct an equipment appraisal impact assessment for each of the modifications and establish an equipment appraisal impact matrix; Step S100: Analyze and summarize one or more of the influence matrices from steps S30 to S90 to obtain the modified cumulative effect analysis and evaluation results.

2. The method according to claim 1, characterized in that, Step S10 includes: The structure and the nuclear island system are analyzed to obtain the list of safety functions.

3. The method according to claim 1, characterized in that, Step S20 includes: Obtain process data on the project initiation, technical analysis, implementation control, and safety evaluation of the modified projects to obtain the modified information. The modified information is integrated according to preset fields to obtain the nuclear power plant modification database.

4. The method according to claim 1, characterized in that, Step S30 includes: Based on the safety function list and the nuclear power plant modification database, each modification is analyzed to obtain the safety functions involved in the modification; Based on the security functions involved in the modification, determine whether the security function list needs to be changed; if so, update the security function list to obtain the list of affected security functions. Based on the list of affected security functions, establish the function impact matrix.

5. The method according to claim 1, characterized in that, Step S40 includes: Based on the list of deterministic safety analysis models for nuclear power plants and the nuclear power plant modification database, each modification is analyzed to obtain a list of affected deterministic safety analysis models involved in the modification. Based on the list of affected deterministic security analysis models, establish the deterministic security analysis impact matrix.

6. The method according to claim 1, characterized in that, Step S50 includes: Based on the list of probabilistic safety analysis models for nuclear power plants and the nuclear power plant modification database, each modification is analyzed to obtain a list of probabilistic safety analysis models affected by the modification. Based on the list of affected probabilistic security analysis models, establish the probabilistic security analysis impact matrix.

7. The method according to claim 1, characterized in that, Step S60 includes: Based on the nuclear power plant disaster assessment list and the nuclear power plant modification database, obtain a list of disaster mitigation measures involved in each modification; The risk mitigation capability of the disaster mitigation measures list is verified by using disaster scenario simulation; Based on the list of disaster mitigation measures and the risk mitigation capabilities, establish the disaster impact matrix.

8. The method according to claim 1, characterized in that, Step S70 includes: The radiation protection impact assessment is conducted on each of the modifications based on the functions of the nuclear power plant's structures, systems, and equipment, and the radiation protection impact matrix is ​​established.

9. The method according to claim 1, characterized in that, Step S80 includes: The impact of each modification on the external radiation environment of the nuclear power plant under normal and accident operating conditions is obtained, and an external radiation environment impact matrix is ​​established.

10. The method according to claim 1, characterized in that, Step S90 includes: Obtain the qualification test of the equipment involved in each of the modifications; Based on each of the aforementioned modifications, an equipment identification impact matrix is ​​established for the identification test.

11. The method according to claim 1, characterized in that, Step S100 includes: Based on the functional impact matrix, security functions affected by two or more modifications are identified; the cumulative effect of the modifications on these security functions is then evaluated based on the functional impact matrix. Based on the deterministic security analysis influence matrix, deterministic security analysis models affected by two or more modifications are selected, and the cumulative effect of modifications on the deterministic security analysis results is calculated. Based on the cumulative effect of modifications on the deterministic security analysis results, the cumulative effect of modifications on the deterministic security analysis models is evaluated. Based on the aforementioned probabilistic security analysis influence matrix, probabilistic security analysis models affected by two or more modifications are selected, and the cumulative probabilistic security analysis results after modification are calculated; the cumulative effect of modification on the probabilistic security analysis models is evaluated based on the cumulative probabilistic security analysis results after modification. Based on the disaster impact matrix, select internal and external disaster mitigation measures that are affected by two or more modifications; evaluate the cumulative effect of the modifications to the internal and external disaster mitigation measures based on the disaster impact matrix; Radiation protection measures affected by two or more modifications are selected based on the radiation protection impact matrix; the cumulative effect of the modifications to the radiation protection measures is evaluated based on the radiation protection impact matrix. Based on the external radiation environment impact matrix, external radiation environment impact indicators and protection measures affected by two or more modifications are screened out; the cumulative effect of the modifications to the external radiation environment is evaluated based on the external radiation environment impact indicators and the protection measures. Based on the device identification impact matrix, device identifications affected by two or more modifications are selected; based on the device identification impact matrix, the cumulative effect of the modifications on the device identification is evaluated; The cumulative effects of modifications to the safety functions, deterministic safety analysis model, probabilistic safety analysis model, measures to resist internal and external disasters, radiation protection measures, external radiation environment, and equipment identification are summarized to obtain risk points, a list of problems, and rectification suggestions as the results of the cumulative effect analysis.

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