FMEA技术在CPR1000机组关键敏感设备维修优化中的应用

结合核电厂维修管理特点形成了简化的失效模式与影响分析即潜在失效模式及后果分析（FMEA）方法,对CPR1000多个机组的关键敏感设备管理（CCM）涉及的设备故障模式、故障影响和维修策略进行了分析,建立了关键敏感设备FMEA数据库。实践证明,该项工作的开展识别出了关键敏感设备未管理到的潜在停机停堆故障模式,发现了关键敏感设备技术文件存在的错误及不一致性,并复核了关键敏感设备清单的正确性和完整性,同时基于群厂运维大数据对众多关键敏感设备维修策略进行了系统性的优化,弥补了关键敏感设备的维修管理不足,减少了不必要的关键敏感设备维修资源投入,对关键敏感设备相关设备管理工作的互助开展,降低核电机组的非计划停机停堆风险有重要参考价值。      

RtCM方法在某核电厂汽水分离再热器系统的应用实践

以可靠性和技术特性为中心的维修(Rt CM)方法是确定资产预防性维修需求、优化维修制度的一种系统工程方法。介绍以Rt CM方法的分析流程和特点,并以某核电厂汽水分离再热器系统为应用试点,详细阐述Rt CM实施过程、设备维修策略优化的效益。实践表明,Rt CM分析方法通过引入故障模板、技术特性分析、设备分级和定量化分析,提高了分析效率,对提高系统设备可靠性发挥了重要作用。     

大亚湾核电站循环水泵维修策略优化分析

利用以可靠性为中心的维修(RCM)分析方法,优化大亚湾核电站循环水泵的维修策略,给出其全面解体检查周期。优化后的解体检查周期远远超过供货商建议的周期(8 a)和国内外同类设备的周期,可有效节约维修成本,并减少与维修活动相关的人因故障。     

电磁阀的失效模式及维修策略

大亚湾和岭澳核电站使用了很多进口电磁阀.随着服役时间不断增加,大量电磁阀出现了漏气、漏油和生锈等故障现象；对这些故障现象进行分类,并结合相关资料分析了电磁阀的工作原理,总结出电磁阀的失效模式；参考法国电力公司(EDF)的维修方法,提出了大亚湾与岭澳核电站电磁阀的维修策略,对相关核电厂电磁阀的维修具有一定的参考价值.     

核电机组长期临停下受影响设备的预防性维修策略动态调整方法研究

针对国内核电厂面临的临时停机(简称临停)现状以及临停所导致的设备可靠性降低的问题,本研究提出了受临停影响设备的预防性维修策略动态调整方法。研究了受临停影响的设备清单识别方法,对受影响设备进行了分类并制定了设备类维修策略模板,最后对维修策略模板进行优化调整后实施应用,并结合具体案例进行了分析说明。结果表明,对受临停影响的设备维修策略进行调整有利于增加受影响设备的运行可靠性和维修有效性,为核电厂长期临停时的设备可靠性分析提供了基础。     

核电厂通风系统防火阀应用现状及维修优化分析

为了提高核电厂防火阀的可靠性，对多个电厂防火阀的应用现状和故障历史进行了梳理，并采用故障模式及影响分析（FMEA）方法对不同防火阀故障机理和维修策略优化进行了研究。结果表明，对年度外观与动作检查任务进行优化，并增加定期更换熔断元件和电动机构任务，有效降低了防火阀故障率，保证了核电厂的安全稳定运行。      

风险指引型技术在核电厂维修策略优化中的应用探索

利用概率安全分析技术来支持核电厂的日常风险管理及安全决策,已成为目前国际上的主流分析方法。本文采用概率论和确定论相结合的风险指引综合决策方法对RRI/SEC热交换器维修策略调整的可行性、合理性和安全影响进行论证,结果表明RRI/SEC热交换器的预防性维修项目可以在功率运行期间实施。应用风险指引型技术对维修策略调整,有助于提高维修工作安排的灵活性、优化大修资源配置、增强维修质量和设备可靠性,对机组安全稳定运行具有重要意义。     

核电厂安全阀维修策略优化研究

目前国内部分核电厂已安全运行十年以上,进入了运行中期阶段,其系统和设备取得了丰富的运行经验和数据积累。现有安全阀维修策略是基于早期的设计经验和设计阶段概率安全评价(PSA)的分析假设。这些假设在很大程度上未反映已运行核电厂的实际运行经验和反馈,以及当前科技发展带来的设备可靠性提高等因素。本文将采用以可靠性为中心的维修(RCM)分析方法针对进入运行中期的核电厂安全阀设备进行维修策略的优化研究。     

可靠性维修在方家山核电机组的开发与应用

秦山核电一厂方家山核电机组是新建的百万级核电机组,用SRCM方法对系统设备实施可靠性管理,开发了SRCM导则,根据电厂性能指标要求进行了SRCM策划、准备、系统关键及重要性分析、设备关键及重要性分析、设备预防性维修大纲编制。在系统关键及重要性分析中,需要确定系统边界、系统功能、分析系统功能故障的后果。设备关键及重要性分析中,需列出设备、识别设备故障模式、识别设备故障影响及后果,并对设备进行分级、分析关键及重要设备故障原因、进行关键、重要设备维修任务选择,对一般级别的设备规定维修的原则。结合实际应用事例阐述SRCM在新建核电厂的开发与应用经验,并提出了SRCM分析过程中亟待解决的问题。     

核电厂维修规则性能指标制定方法研究

为提高核电厂维修的有效性和风险管理水平,国家核安全局2017年发布了《改进核电厂维修有效性的技术政策(试行)》,要求试点核电厂逐步开展相关的维修活动优化研究。技术政策中提出性能指标的目的是对纳入维修规则范围的构筑物、系统和设备分别制定合适的可测量参数以对其性能趋势进行客观的判断。本文对现阶段适用于核电厂的"确定风险重要类"和"制定性能指标"方法进行研究,提出确定风险重要类的判断方法和示例,分析了不同风险重要度组合对维修策略的影响,介绍了采用二项式分布和泊松分布确定性能指标的方法和示例,为国内维修规则试点工程提供相应技术参考。     

RAMI analysis of the ITER CIS

ITER is the first worldwide international project aiming to design a device that proves the physics and technological basis for fusion power plants to produce nuclear fusion energy. In the project, the RAMI approach (reliability, availability, maintainability and inspectability) has been adopted for technical risk control to guide the design of components in preparation for operation and maintenance. RAMI analysis of the ITER central interlock system (CIS), which shall provide investment protection for the ITER systems was performed on the conceptual design. A functional breakdown was prepared in a bottom-up approach, resulting in the system being divided into 5 main functions and 7 sub-functions which are described using the IDEFØ method. Reliability block diagrams (RBDs) were prepared to estimate the reliability and availability of each function under stipulated operating conditions. Initial and expected scenarios were analyzed to define risk-mitigation actions. The inherent availability of the ITER CIS expected after implementation of mitigating actions was calculated to be 99.86% over 2 years, which is the typical interval of the scheduled maintenance cycles. A failure modes, effects and criticality analysis (FMECA) was performed to initiate risk mitigation action. Criticality matrices highlight the risks of the different failure modes with regard to the probability of their occurrence and impact on operations. It was assessed that the availability of the ITER CIS, with appropriate mitigating actions applied, meets the project availability requirement for the system.     

保护系统下试验期间开关故障导致机组瞬态的故障分析及优化

秦山第二核电厂反应堆保护系统进行模拟量通道试验（T1试验）时，由于开关故障导致信号未被切除，导致机组瞬态故障。本文针对试验期间开关故障导致机组瞬态故障为出发点，对开关本体进行剖析，提出开关切换验证的办法，并结合工作实践提出了优化的维修策略，有效地保障了机组安全稳定运行。      

Decision-Making Support Systems for Reliability-Centered Maintenance

Abstract

A Systematic Reliability Improvement (SRI) program has been developed to support the decision-making processes of preventive maintenance (PM) planning for enhancing plant/system reliability in nuclear power plants. The SRI program is based on improved information-handling methods in the Reliability-Centered Maintenance (RCM) methodology. This program enables us to select a proper PM plan using a computerized system that integrates the following three subsystems which have been developed and is implemented on an engineering work station.

(1) The maintenance management support subsystem can provide statistical parameters which indicate the characteristics of the failure mode for components based on the statistical analysis of field maintenance data.

(2) The FME/CA-database subsystem can manage the system/component failure modes and their characteristics which are estimated by experts at the design stage using 13 types of assessment rankings of the failure mode effects and criticality analysis (FME/CA).

(3) The PM planning support subsystem can support decision-making in determining the priority of PM improvement plans using a new method combining the above FME/CA assessment rankings and interactive logic tree analysis (I-LTA).

The effectiveness of the SRI program and its support systems has been validated through a feasibility study using simulated data on a primary loop recirculation system in BWR plants.     

Airline experience with reliability-centered maintenance

Reliability-Centered Maintenance is a process for developing preventive maintenance programs. Its concepts evolved from the post WWII experience of the airline community. Its genesis was in a paper by F. Stanley Nowlan and Thomas D. Matteson of United Airlines for the American Institute of Aeronautics and Astronautics in 1967. Its first application was to the Boeing 747. It has subsequently been adopted by the FAA and the Department of Defense and applied to many new transport and military aircraft. Its objective is applicable and effective preventive maintenance and it has proven to be a highly effective replacement for the prior intuitive processes for selecting preventive maintenance tasks. It focuses on system functions, functional failures, then dominant failure modes and effects. It then uses a decision tree to classify failure criticality and identify applicable and effective tasks. The result is a program focused on maintaining inherent safety and reliability at minimum cost.     

基于最优化线抽样法的XAPR自然循环功能失效研究与分析

针对多维不确定性参数、小失效概率的功能可靠性分析,提出了一种优化线抽样的可靠性分析方法。该方法采用遗传算法求解约束条件的优化模型来寻求最优化重要方向,进而得到失效概率的高效估计。以西安脉冲堆（XAPR）自然循环冷却堆芯能力的可靠性评价为例,考虑模型与输入参数的不确定性,对中破口失水事故下的自然循环功能失效概率进行了量化分析。结果表明：与其他概率评估方法相比,本文方法具有很高的计算效率,同时又能保证很好的计算精度;对隐式非线性的功能可靠性分析是有效可行的,具有很强的适应性。     

A genetic algorithm solution for a nuclear power plant risk–cost maintenance model

Reliability Centered Maintenance (RCM) is one of the popular maintenance optimization methods according to certain kinds of priorities. Traditional RCM usually analyzes and optimizes the maintenance strategy from the viewpoint of component instead of the whole maintenance program impact. Research presented in this paper is a pilot study using PSA techniques in RCM. How to reflect the effect on component unavailability by the maintenance activities such as surveillance testing and preventive maintenance in PSA model is discussed firstly. Based on the discussion, a maintenance risk–cost model is established for global maintenance optimization in a nuclear power plant, and a genetic algorithm (GA) is applied to solve such a model to get the global optimized maintenance strategy. Finally, the result got from a simple test case based on a risk–cost model consisting of 10 components is presented.     

Evaluation of the dependencies related to passive system failure

A major issue to be addressed in safety and risk studies related to advanced reactors is the reliability of the implemented passive safety features. The passive safety system operation is a quite complex process. This complexity gives rise to unpredictable failure patterns. While there are a number of well-established failure analysis (physics-of-failure) models for individual components, these models do not hold good for complex systems as their failure behaviours may be totally different. Failure analysis of individual components does consider the environmental interactions but is unable to capture the system interaction effects on failure behaviour. These models are based on the assumption of independent failure mechanisms. Dependency relationships and interactions of components in a complex system might give rise to some new types of failures that are not considered during the individual failure analysis of that component.The approach to the passive system reliability assessment based on independent modes of failure begins by identifying critical parameters, as input to basic events, corresponding to the failure modes, arranged in a series system configuration. Within this methodology, the selected system critical parameters are properly modelled through the construction of probability functions. The application of the methodology to a realistic thermal-hydraulic passive system design is illustrated. The analysis reveals that the critical parameters are not suitable to be chosen independently of each other, mainly because of the expected synergism between the different phenomena under investigation, with the potential to jeopardize the system performance. This conclusion allows the implementation of the proposed methodology, by properly capturing the interaction between various failure modes.     

Quantification of unavailability caused by random failures and maintenance human errors in nuclear power plants

Risk analysis of any equipment or system estimates the unavailability of redundant components due to hardware failure, periodic test and repair work, and human errors in maintenance tasks. A model has been developed in this study to estimate the unavailability of a periodically repairable component of a system that considers hardware failure and maintenance errors due to human failure, and which is applicable to estimate system unavailability in nuclear power plants as well as other industries. A sensitivity analysis has been performed based on the newly developed model considering multiple levels of human errors in maintenance tasks to observe the effects of maintenance errors on overall unavailability of a component. The effect of human error on the optimal frequency of periodic maintenance of a device has been analyzed based on the newly developed unavailability quantification model.