Evaluation of risk and cost using an age-dependent unavailability modelling of test and maintenance for standby components

The improvement of safety in the process industries is related to assessment and reduction of risk in a cost-effective manner. This paper addresses the trade-off between risk and cost related to standby safety systems. An age-dependent unavailability model that integrates the effects of the test and maintenance (T&M) activities as well as component ageing is developed and represents the basis for calculating risk. The repair “same-as-new” process is considered regarding the T&M activities. Costs are expressed as a function of the selected risk measure. The time-averaged function of the selected risk measure is obtained from probabilistic safety assessment, i.e. the fault tree analysis. This function is further extended with inclusion of additional parameters related to T&M activities as well as ageing parameters related to component ageing. In that sense, a new model of system unavailability, incorporating component ageing and T&M costs, is presented. The testing strategy is also addressed. Sequential and staggered testings are compared. The developed approach is applied on a standard safety system in nuclear power plant although the method is applicable to standby safety systems that are tested and maintained in other industries as well. The results show that the risk-informed surveillance requirements differ from existing ones in technical specifications, which are deterministically based. Moreover, the presented approach achieves a significant reduction in system unavailability over a relatively small increase of total T&M costs.     

Uncertainty analysis in the nuclear industry: Analytical unavailability modelling incorporating ageing of safety components

There is a growing interest in analyzing the possibility for current nuclear power plants operation extension. In that sense, life management programs, considering safety components ageing, are being developed and employed. On the other side, the large uncertainties of the ageing parameters as well as the uncertainties associated with most of the reliability data collections are widely acknowledged.This paper deals with uncertainty analysis associated with specific ageing rates database. The analysis is conducted using an analytical unavailability model applied for a selected safety system in a nuclear power plant. The most important problem is the immense uncertainty associated to the component ageing data sets as well as the lack of the very data in general, which would correspond to the more detailed modelling of ageing.New probability distributions, encompassing the ageing rates available in the considered data set, are suggested. The obtained results indicate the extent to which the uncertainty of the considered ageing data set, given the inherently assigned probability distribution, influences the performed unavailability calculations. Additionally, comparative analysis regarding the insights gained out of the application of the suggested probability distributions is conducted.     

基于风险指引的核电厂设计改进评价研究

核电厂概率安全评价(PSA)可以论证核电厂的风险满足安全目标,也是对运行核电厂进行风险管理的有效工具,例如核电厂的在役检查、安全分级、技术规格书优化等。核电厂的风险指引管理是在确定论的基础上,充分利用概率安全评价的结果进行风险影响评价,以此来论证决策的合理性。核电厂的重要设计改进通常基于传统的工程分析结果,没有分析其对核电厂整体风险的影响。重点探讨风险指引决策的基本原则以及方法,以核电厂设计改进实例探讨如何在分析时引入风险指引方法,并提出相关建议。     

核电厂起重机安全监控管理系统的应用

本文从法规的要求和核电厂设备运行管理需求两方面介绍核电厂起重机增加安全监控管理系统的必要性,并以核电厂主行车安全监控管理系统为例,介绍了核电厂起重机安全监控管理系统的基本原理和系统构造,阐述了核电厂安全监控管理系统在国标要求基础上进行的设计提升和应用情况,为行业起重机尤其后续新建核电厂起重机安全监控管理系统的设计、验收...     

Dynamic management of human error to reduce total risk

Safety management in companies at the limit of risk criteria must be implemented in order to survive in the very aggressive and competitive environment of modern society. It implies that the risk in process industries is crossing the limit of safe practices. Most major accidents consist of human errors and mechanical component failures, and cannot be explained by a stochastic coincidence of independent events. This work focuses on the coincidence of human error and mechanical failure to introduce a concept of dynamic management of human error. By the dynamic management of human error during a short period, when a mechanical component is temporarily unavailable during periodic testing or maintenance, the probability of a major accident may be reduced significantly without additional investment on improving safety. For the periodically-tested standby component, the majority of total average unavailability of the component may be recognized by operators or workers as well as maintenance mechanics. During this short period, an appropriate dynamic management of human error for improving human performance temporarily may be very effective in reducing total risk in industries. The dynamic management of human error may be a useful method to prevent loss effectively in the process industries     

维修时间不确定性下配电网灾后维修队安排的鲁棒恢复研究*

为最小化灾后配电网损失量,准确描述完整维修队工作时间（分为路途时间与具体维修时间）,依据台风路径对维修队所需路途时间进行分类,并利用期望概率描述具体维修时间的不确定性。建立2阶段分布式鲁棒优化模型,采用CCG算法分析国内某地区配电网算例发现:考虑维修时间不确定性可以有效减少配电网损失量。     

A framework to estimate the risk-based shutdown interval for a processing plant

Petrochemical plants and refineries consist of hundreds of pieces of complex equipment and machinery that run under rigorous operating conditions and are subjected to deterioration over time due to aging, wear, corrosion, erosion, fatigue and other reasons. These devices operate under extreme operating pressures and temperatures, and any failure may result in huge financial consequences for the operating company. To minimize the risk and to maintain operational reliability and availability, companies adopt various maintenance strategies. Shutdown or turnaround maintenance is one such strategy. In general, shutdown for inspection and maintenance is based on the original equipment manufacturer's (OEM) suggested recommended periods. However, this may not be the most optimum strategy given that operating conditions may vary significantly from company to company.The framework proposed in this work estimates the risk-based shutdown interval for inspection and maintenance. It provides a tool for maintenance planning and decision making by considering the probability of the equipment or system for failure and the likely consequences that may follow. The novel risk-based approach is compared with the conventional fixed interval approach. This former approach, characterized as it is by optimized inspection, maintenance and risk management, leads to extended intervals between shutdowns. The result is the increase in production and the consequent income of millions of dollars.The proposed framework is a cost effective way to minimize the overall financial risk for asset inspection and maintenance while fulfilling safety and availability requirements.     

新形势下的核安全与辐射安全对策

随着核资源广泛利用,核安全也越来越受到人们的关注。笔者在新的安全形势下,从实际情况出发,分析了我国核和辐射安全现状,特别是近年来,世界范围内核恐怖事件的潜在危险在不断增加,核设施和辐射设施在运行过程中,由于失误等原因引起事故的可能性是客观存在的,在现代战争条件下,核设施极有可能成为敌人精确打击的战略目标,因此,核安全和辐射安全面临着新的挑战。针对核安全和辐射安全存在的隐患,应从应急组织体系建设、监测系统开发、人员培训、基本信息数据库的建立、应急决策支持系统开发、完善法规、加强国际合作等方面,提出了改善我国核安全与辐射安全现状的相关对策,以不断提高我国核安全和辐射安全的水平。     

安全联锁设备SIL验证中的参数估计偏差分析*

为提高安全联锁系统（SIS）不可用度计算的准确性,减少SIL验证的不确定性偏差,研究参数估计置信度分别为70%和90%时功能安全标准IEC61508的恒定失效率算法与实际非恒定失效率（威布尔分布）算法结果的偏差。结果表明:在70%置信度时,采用指数分布算法计算PFDavg,比威布尔分布算法的计算结果偏大,2者的相对偏差平均值为68.01%;90%置信度时,2者的相对偏差平均值为42.63%,揭示功能安全标准IEC61508恒定失效率计算将显著高估SIS的不可用性,可能造成企业不必要的整改和相应的维护成本。     

Equipment selection for the optimal system unavailability of jacketed reactors with discrete cost data

This study introduces a method that selects equipment, so as to reach the required unavailability level, by carrying out an optimization analysis which considers the reliability data and cost of the equipment. A more practical optimization problem has been formulated using the objective function based on the discrete function and constraints.For the cooling system of a jacketed reactor, an optimization analysis was performed on equipment that have different failure rates depending on their costs in order to reach the target unavailability level required by the system. The integer programming was used for this optimization analysis. When the method developed through this study is used, cost can be reduced and the target level of the system unavailability can be reached by selecting proper equipment for chemical plants through the optimization analysis. This is more cost efficient than the former method of selection, which does not perform any economical analysis thus leading to the usage of overly expensive equipment with low failure rates.     

核电站事故前人因可靠性分析方法

人因可靠性分析 (HRA)已成为概率安全分析 (PSA)必不可少的内容 ,事故前人因事件可靠性分析对有效预防维修、调校工作中的人因失误有着重要作用 ,是人因可靠性分析的重要组成部分 ,对PSA最终计算结果有重要影响。笔者结合核电站人因可靠性分析的实际需求 ,运用了以THERP为主的人因失误概率评价方法 ,创建了事故前人因事件分析的基本程序、方法及分析文档模式 ,表述了程序化的事故前人因事件分析模式 ,为我国核电站事故前人因可靠性分析提供了完整和有效的分析方法 ,并有效用于秦山核电站的PSA。     

核电站FDA安全管理信息流系统模型的构建研究

为了从安全信息的角度完善核电站的事故致因机理,并在实践中加强核电站的安全管理,首先以安全信息为视角,以系统安全行为链为主线,建立核电站FDA安全管理信息流系统模型,该模型由运行操作人员、核电站企业、国家核安全局3条子链和1条必要安全信息主链构成;然后结合模型和核电站具体工作流程,分析得到3个子事故域和1个总事故域,并归纳出核电站安全运行各阶段所需的必要安全信息;最后结合事故域,分析模型在核电站安全管理中的实际应用价值。     

电力生产班组安全管理能力成熟度模型研究

根据事故案例及统计数据,分析得出提升电力生产班组安全管理能力是提高电力生产企业安全管理水平、维护人员和设备安全的重要途径。将系统理论引入电力生产班组安全管理能力研究,将电力生产看做一个动态的过程,把握住人、机、环境三大要素,以增量方式逐步引入三要素的发展变化,建立起生产班组安全管理能力成熟度5级模型:初始级、可重复级、已定义级、已管理级、改进优化级。只有达到上一级人、机、环境所要求的指标,安全管理能力成熟度可达上一级,电力生产班组可按一系列小的改良性步骤向更高的成熟度等级前进。安全管理能力成熟度达到改进优化级的电力生产班组可自发的不断改进,防止同类缺陷二次出现。     

Importance and uncertainty analysis of flue gas scrubber systems with extreme reliability parameter values

Although reliability analyses have been used to improve the reliability of industrial systems, generic reliability data from publications, such as component failure intensities and repair times, are used to calculate reliability measures instead of the real reliability data collected from the plant. One reason is that the repair history of the components is not well managed in the plant. In this work, the effect of extreme reliability parameter values on system reliability and unavailability is studied. To do this, importance and uncertainty analysis of the components of flue gas scrubber systems is carried out, and results calculated with the extreme reliability parameter values are compared with those with the mean reliability values of the systems. The different reliability parameter values can give us totally different ranks of the components critical to the reliability of the representative scrubber system. Consequently, the effort to establish a reliable database is emphasized to perform accurate reliability analysis of the system.     

核电厂人因事故预防的定量化决策

人因事故的分析与预防是核电厂安全运行和管理的重要内容。笔者提出的系统安全性层次分析法主要从两种角度考虑系统的安全性:专家能力权值和安全性矩阵的建立。采用专家判断矩阵确定事故原因对系统安全性的重要度排序。举例某核电厂事故定量分析进行说明,在对事故进行原因分析基础上,构建事故影响因素层次模型,利用层次分析法分析得出事故原因重要度排序由高到低依次为组织管理、操作人员、人机界面、培训与设备状态,并据此提出了相应的预防与改进措施,为安全性要求较高的复杂工业系统提供事故预防的定量化决策依据。     

基于模糊贴近度和熵权的航空装备维修安全综合评价

航空装备维修安全是确保装备飞行安全的重要因素,为提高航空装备飞行的安全性,需要对航空装备维修安全进行准确评价。根据航空装备维修安全评价涉及的不确定性问题,采用模糊数学和熵理论,提出一种基于模糊贴近度和熵权的航空装备维修安全综合评价方法。在建立航空装备维修安全评价指标体系的基础上,采用熵确定各指标的权重值、加权平均算子确定综合评价集,利用非对称贴近度进行决策分析。通过对某型飞机调查数据的算例分析,确定航空装备维修安全的主要影响因素,得出该型飞机维修安全水平的评价值。     

基于模糊贴近度的组织安全文化评估方法

鉴于组织安全文化评估过程中,各因素指标及其相互作用关系具有模糊性,引入模糊数学理论,提出一种基于模糊贴近度的组织安全文化评估(SCA)方法。首先,构建组织安全文化因素指标体系以及确定SCA特征状态模式;其次,依据模糊语言隶属度函数以及特征状态模式,确定指标与SCA等级的隶属度;第三,确定指标与各等级的非对称贴近度,依据模糊贴近度判断矩阵进行评估决策;最后,以核电组织安全文化为例,通过对比分析进行方法的验证。实例分析结果的一致性表明:该方法能有效量化系统状态与各评估等级之间的贴近程度,能解决安全文化以及评估状态的模糊性问题,且评估结果与实际状态相吻合。     

我国游乐设施安全法规体系的建立与分析

从我国游乐设施相关法律、法规、规章、技术规范和技术标准5个层次入手,梳理并分析了我国目前游乐设施安全法规与技术标准体系,针对游乐设施法律的欠缺、安全技术规范不能涵盖全部游乐设施及其安全监察、游乐设施的设计理念偏颇、现有游乐设施法规标准对游乐设施的一些要求与国际不接轨且量化要求不足等问题,笔者提出了国家应尽快制定颁布《特种设备安全法》或游乐设施的相关法律,早日填补游乐设施在型式试验、安全评价、评估、寿命预测、预警和进出口大型游乐设施监督管理办法的安全技术规范空白,改变游乐设施设计理念,完善游乐设施安全技术规范和技术标准的量化要求,尽快使我国游乐设施安全法规与技术标准体系适应国情并与国际体系接轨。     

基于层次分析方法的核电火灾风险评估研究

核电火灾是现代消防安全的重要部分。依据核电厂的实际组成构造对其进行了层次划分,建立了由堆本体、一次冷却系统、化容控式系统堆安全系统、汽轮发电机组和燃料操作系统为中间层的核电火灾危险性评价指标体系。结合收集到的相关核电事故数据资料,运用层次分析法对核电厂各系统部位引发火灾造成的核电安全风险进行了评估,确定了各组分的统计权重,得到了针对核电厂各构造部位的火灾危险性层次评价模型。并利用评价打分的方法对核电厂进行调查模拟评价,计算出核电厂各组成部分消防安全状况的危险指数,所得结果比较符合核电火灾实际统计。     

核电站重要敏感性设备分析

核电站重要敏感性设备管理是国内首次采用归纳法和演绎法对核电站重要敏感系统和设备进行识别和设备分级的一种新方法。目标是为了找到导致反应堆紧急停堆、强迫停机和非计划跳机跳堆风险的主要部件 ,并采用 80 - 2 0的原理进行有效的管理 ,建立有效的风险管理 (预防、探测、改正行动 PDC ,Prevention/Detec tion/Correction)大纲和PDC管理数据库 ,并对大部分的重要敏感设备的子部件进行的FMEA(FailureModeandEffectAnalysis)分析 ,识别其失效机理 ,从而确定重要敏感设备清单和预防跳机跳堆的改正行动 ,减少未来由于设备失效导致的跳堆次数 ,达到提高核电站的设备可靠性、安全性和经济性的目的。