AP1000非能动余热排出系统可靠性与概率安全评价模型的融合

研究AP1000非能动余热排出系统可靠性,应用重要度和敏感性指标全面详细地分析系统设备可靠性,得到导致系统失效的设备各种失效模式的重要度和敏感性排序结果;整合了系统设备可靠性与物理过程可靠性,将整体可靠性融合进概率安全评价模型。分析结果表明:研究非能动余热排出系统可靠性时不仅需要分析其设备可靠性,还应该重点考虑系统物理过程可靠性,应整合两种可靠性并将系统整体可靠性融合进概率安全评价模型,综合分析非能动余热排出系统可靠性。     

基于PSA的非能动余热排出系统可靠性研究

非能动型反应堆概率安全评价（PSA）工作在分析非能动系统可靠性时，仅考虑系统设备可靠性，未涉及物理过程可靠性。综合考虑非能动系统设备可靠性与物理过程可靠性时，又存在仅考虑系统投入的设备可靠性而忽略运行设备可靠性的问题。针对此问题，以丧失正常给水事故下AP1000非能动余热排出系统（PRHRS）为研究对象，采用自主提出的综合法将系统可靠性融合进PSA模型，兼顾能动设备的需求失效与非能动设备的运行失效，分析了系统设备可靠性的敏感性。结果表明，综合法对PRHRS进行可靠性分析时所得事故序列谱更真实、更全面，与传统方法相比较具有优越性。      

非能动安全系统可靠性评估方法初步研究

非能动安全系统可靠性的分析是广泛采用非能动设计的新一代核电厂概率安全评价(PSA)的重要内容,其量化分析需根据非能动安全系统可靠性评估对象,确定影响系统运行的关键参数,结合事件序列对非能动系统进行研究。本文以AP1000非能动余热排出系统(PRHRS)设计阶段的可靠性研究为例,结合丧失主给水事故,根据燃料包壳完整性以及系统稳定性的功能准则,确定影响PRHRS的关键参数和设计参数。采用拉丁超立方抽样(LHS)确定输入参数组合,运用RELAP5/MOD3程序进行不确定性传递计算,进行关键参数对系统功能敏感性评价与确认,进行系统功能可靠性分析,为AP1000概率安全评价提供PRHRS可靠性估计。     

非能动系统可靠性评价方法综述

随着非能动系统在核电站中实际应用,非能动系统可靠性分析也逐渐成为电厂概率安全评价的重要内容,国际上针对该问题开展了大量研究工作,并形成了几种评价非能动系统可靠性评价的方法。本文章简要介绍几种非能动系统可靠性评价方法,对各种方法进行了比较,并结合目前研究现状,对今后的研究工作提出了一些展望。     

核动力装置非能动系统可靠性及参数敏感性分析

在非能动安全功能可靠性方法(RMPS)框架下,对某型核动力装置非能动余热排出系统原理性试验系统的热工水力可靠性(TH-R)进行评估,并对影响系统可靠性的不确定性参数进行敏感性分析。相关结论有助于从可靠性角度增强对该非能动余热排出系统热工水力过程不确定性的认识,可用于指导系统的设计优化及运行管理。     

非能动自然循环技术的发展与研究

非能动技术在核电工程领域越来越受重视，文章列举了非能动自然循环在核电系统中的应用，对其在运行过程中可能存在的问题进行了分析。介绍了非能动自然循环可靠性分析目前的数学研究方法，并简要总结了这些方法的优缺点。最后展望了非能动自然循环的发展方向。由于非能动自然循环存在失效的可能，在系统运行过程中应对非能动自然循环物理过程失效及其可靠性予以足够重视和积极研究；为了确保系统运行的安全性，系统运行过程中要能动与非能动相互结合，同时选择精确模型，完善非能动可靠性分析方法，准确实现理论计算与实验验证。     

拉丁超立方抽样在非能动系统可靠性分析中的应用与发展

拉丁超立方抽样(Latin Hypercube Sampling,LHS)方法具有较好的空间填充特性和良好的概率性质,广泛应用于计算机仿真领域,以解决复杂系统计算机仿真的巨大运算代价问题和复杂系统的精确替代模型建立问题。本文介绍了LHS方法在非能动系统可靠性分析中的优势,综述了LHS的改进方法、优化方法及样本扩展方法,给出LHS方法在核能领域的应用及存在的问题。最后,指出LHS方法应用于非能动系统可靠性分析中的发展趋势与方向。     

核电厂非能动余热排出系统的失效概率评价

先进核电厂设计中大量采用非能动安全系统提高反应堆安全性。但目前尚无系统性评价非能动系统的成熟方法,而且概率安全评价(PSA)也未考虑非能动系统自然循环现象不确定性导致的功能失效。在欧盟非能动系统可靠性评价研究项目(RMPS)研究成果的基础上,以压水堆二次侧非能动余热排出系统(PRS)为研究对象,基于统计学和热工水力计算确定了影响性能的参数重要度,进而利用蒙特卡罗抽样和响应面分析对全厂断电事故下的PRS自然循环失效概率进行了量化分析评价。初步评价结果表明:非能动系统功能失效概率为2.14×10-3,在PSA中应当充分考虑各种非能动系统的功能失效。本文的评价方法还可以为非能动安全系统设计优化提供支持。     

非能动系统可靠性分析方法在AP1000非能动ERVC系统中的应用

由于核电厂安全水平要求的逐渐提高,越来越多的非能动系统被用于先进反应堆堆型中,但对这些非能动系统可靠性评价的工作还处于初级阶段。本文根据非能动系统可靠性评价流程,通过RELAP5热工水力学程序模拟非能动系统物理过程,对AP1000反应堆压力容器外部冷却（ERVC）系统进行了可靠性评价。通过计算得到了压力容器下封头温度等参数的累积密度分布曲线,根据不同的成功准则即可获得AP1000 ERVC系统的可靠性。该非能动系统可靠性评价结果可用于核电厂PSA模型中,以更好地指导核电厂设计及提高核电厂的安全性。     

基于GO-FLOW方法的非能动安注系统可靠性分析研究

研究了GO-FLOW方法及其应用特点,给出GO-FLOW方法在系统可靠性分析中的特点;研究非能动安全注入系统在DVI管线破裂事故中的响应特点,给出事故缓解中安注系统的成功准则及投入序列;建立系统的GO-FLOW模型,完成非能动安注系统在DVI管线破裂事故中的可靠分析,得到系统在不同时间点的可靠性数据;对GO-FLOW方法和故障树方法的计算结果进行对比,找出其结果差异的原因,分析两种方法的计算特点,得出两种方法在系统可靠性评价中的应用特点。     

Uncertainties associated with the reliability of thermal-hydraulic nuclear passive systems

ABSTRACT

The increasing adoption of passive safety based front-line systems in advanced nuclear power reactors due to their simplicity, cost competitiveness and autonomous nature makes it very essential to carefully consider the uncertainties associated with their behaviour and the phenomena linked to their operations. The passive safety systems (PSSs) are known to be characterized with several uncertainties in their modelling and operations. These uncertainties are usually more pronounced than those of their active systems counterparts due to the stochastic nature of the associated phenomena, insufficient knowledge of their physics of operation and inadequacy of relevant real/experimental data. This paper thus focused on the uncertainty issues of the thermal-hydraulic (t-h) PSSs which influence their reliability analysis. In addition, the inadequacies of previous research, current research challenges and likely future research directions on uncertainties associated with the models and phenomena applicable to the t-h PSSs adopted in advanced reactors were discussed. For the purpose of illustration, Weibull distribution was adopted for the failures associated with a generic passively cooled steam generator and Bayesian approach applied to account for phenomenological uncertainty. The output of the approach justified the need to account for epistemic uncertainty in reliability analysis of such systems.     

CARR应急供电系统可靠性分析

应急供电系统是保证中国先进研究堆（CARR）安全的重要系统之一,它的高可靠性是保证其完成预期功能的重要条件。本文以应急供电系统为研究对象,利用故障模式及影响分析和故障树等可靠性分析方法,建立相应模型,对应急供电系统进行定性和定量的分析,得到了该系统发生故障的概率和最小割集,找出了薄弱环节,提出了有效提高该系统可靠性的建议和措施,为保证CARR安全可靠地运行提供支撑。     

灵敏度分析方法在非能动系统可靠性研究中的应用

在研究核电站安全时,热工水力非能动系统的可靠性研究基于所建立的热工水力学数值模型。模型通常极其复杂,具有多个输入参数,且输入参数具有不确定性,对模型输出的不确定性的影响又各不相同。灵敏度分析的目的是将各参数对模型输出的不确定性的影响进行排序,找出显著的影响参数。本文首先描述灵敏度分析的方法,然后应用秩转换回归分析方法计算HTR-10余热排出系统模型各参数的灵敏度,找出关键影响因素,将模型简化,并对简化模型应用响应面方法计算了失效概率。简化模型算得的失效概率与原模型的很接近。     

XAPR中破口失水事故下堆芯自然循环冷却能力的功能可靠性研究

功能失效是导致自然循环系统运行失效的重要因素，需在其可靠性分析中予以考虑。针对多维不确定性参数及小功能失效概率问题，提出了一种将改进响应面法及重要抽样子集模拟法相结合的功能可靠性分析方法。以西安脉冲堆（XAPR）堆池水自然循环冷却为例，结合中破口失水事故，考虑输入参数及模型的不确定性，对其进行了功能可靠性评估和灵敏度分析。结果表明：XAPR堆芯自然循环功能失效概率为3.796×10^-3，需充分考虑系统功能的可靠性。本文方法具有较高的计算效率，同时又能保证很高的计算精度，对XAPR堆芯自然循环非线性功能函数具有很强的适应性。     

Screening of critical parameters influencing thermal-hydraulic reliability of simple passive system

Robust safety nature of passive safety systems (PSSs) accounts for their increasing applications. Critical parameters (CPs) which influence reliability of thermal-hydraulic (t-h) PSSs are considered independent in most cases while considering their effects purposely for simplicity which may not be realistic. Findings affirmed reliability of t-h PSSs to be influenced by CPs that are dependent in most scenarios and thus, effects of CPs dependency which can directly/indirectly influence t-h reliability need to be considered. Reliability assessment methodologies (RAM) can thus be improved upon by considering the dependency of CPs in reliability analysis. In this regard, this paper considers the screening of CPs required to justify their dependency consideration in evaluating t-h reliability. The Pearson’s product moment correlation coefficient and covariance method were applied as illustration for the screening of the possible realistic CPs, which affect natural circulation of a passively water-cooled steam generator. The approach was used to determine the combinations of the CPs that are dependent and screens out those adjudged independent. Based on the results obtained, appropriate considerations (dependency/independency) can be made and further analysis of interest (failure/reliability) can be conducted for the system. Incorporation of this screening approach into the existing t-h RAMs will improve their efficiency.     

Quantitative dynamic reliability evaluation of AP1000 passive safety systems by using FMEA and GO-FLOW methodology

The passive safety systems utilized in advanced pressurized water reactor (PWR) design such as AP1000 should be more reliable than that of active safety systems of conventional PWR by less possible opportunities of hardware failures and human errors (less human intervention). The objectives of present study are to evaluate the dynamic reliability of AP1000 plant in order to check the effectiveness of passive safety systems by comparing the reliability-related issues with that of active safety systems in the event of the big accidents. How should the dynamic reliability of passive safety systems properly evaluated? And then what will be the comparison of reliability results of AP1000 passive safety systems with the active safety systems of conventional PWR.

For this purpose, a single loop model of AP1000 passive core cooling system (PXS) and passive containment cooling system (PCCS) are assumed separately for quantitative reliability evaluation. The transient behaviors of these passive safety systems are taken under the large break loss-of-coolant accident in the cold leg. The analysis is made by utilizing the qualitative method failure mode and effect analysis in order to identify the potential failure mode and success-oriented reliability analysis tool called GO-FLOW for quantitative reliability evaluation. The GO-FLOW analysis has been conducted separately for PXS and PCCS systems under the same accident. The analysis results show that reliability of AP1000 passive safety systems (PXS and PCCS) is increased due to redundancies and diversity of passive safety subsystems and components, and four stages automatic depressurization system is the key subsystem for successful actuation of PXS and PCCS system. The reliability results of PCCS system of AP1000 are more reliable than that of the containment spray system of conventional PWR. And also GO-FLOW method can be utilized for reliability evaluation of passive safety systems.     

CARR保护系统可靠性分析

保护系统是保证中国先进研究堆（CARR）安全的重要系统之一，它的高可靠性是保证其完成预期功能的重要条件。本工作以保护系统为研究对象，利用故障模式及影响分析和故障树等可靠性分析方法，建立相应模型，对保护系统进行了定性和定量的分析，得到了保护系统发生故障的概率和最小割集，其可靠性水平达到了CARR工程的设计要求，验证了设计，为CARR其他系统分析和验证奠定了基础。