大事件树法船用核动力装置中小破口失水事故评价

分析了满功率工况下船用核动力中小破口失水事故后安全功能需求、系统响应和操纵人员干预对堆芯损毁的影响,在对前沿系统和支持系统分析和简化的基础上,采用大事件树/小故障树方法建立了事故序列化模型.通过量化分析,找出了始发事件下导致堆芯损毁的支配性序列、支配性题头事件,提出了系统改进的建议.     

西安脉冲堆满功率运行工况内部始发事件一级概率安全评价

针对西安脉冲堆(XAPR)2 MW满功率运行工况,建立了内部始发事件一级概率安全评价(PSA)模型,对始发事件识别、事故序列分析及可靠性数据处理等进行了研究。应用小事件树-大故障树方法,在Risk Spectrum平台上完成XAPR堆芯损伤事故序列的定量分析。结果表明,XAPR内部事件导致的堆芯损伤频率(CDF)为4.14×10~(-6)/(堆·年),对CDF贡献最大的为堆水池堆芯高度处大破口失水事故,支配性事故序列是大破口失水事故后紧急排水系统失效。研究结果证明XAPR具有较高的安全性。     

基于结构重用的事件树复杂边界条件处理方法

事件树分析是核电厂概率安全分析中最常用的方法之一,在运用该方法进行定性定量分析时首先需要将模型中的序列/后果链接形成相应的序列/后果故障树,该过程中一般通过边界条件和成功分支处理准则等设置来保证最终故障树达到指定要求。为解决由于复杂边界条件设置导致的最终故障树结构冗余问题,本文提出了一种基于结构重用的事件树复杂边界条件处理方法。经大量实例验证,该方法完全正确,可显著提高概率安全分析软件事件树分析速度,并为核电厂的实时风险分析提供了技术基础。     

中国实验快堆一回路冷阱工艺间钠火概率安全评价

本文运用事件树方法对中国实验快堆一回路冷阱工艺间发生钠火后的事故场景进行演绎分析,运用故障树方法对钠火相关系统进行可靠性建模。在此基础上计算得到各钠火事故序列的条件发生概率。结果表明:在获得的25个典型钠火事故序列中,19个序列的条件发生概率较低;在发生概率相对较高的6个序列中,4个序列的后果轻微,其余两个序列代表的钠火场景存在一定不确定性,需要在今后的钠火危险性评价中进一步具体研究。     

秦山二期扩建工程PSA项目工作任务分析

参照新版HAF102的要求，秦山二期扩建工程设计中将应用概率安全分析(PSA)方法作为确定论分析方法的辅助和补充。本文简要介绍了秦山二期扩建工程PSA项目的工作目标和工作范围，并详细分析了PSA项目的具体工作任务，即1级PSA和简化的2级PSA。1级PSA的工作任务包括始发事件的定义和选取、事件树分析、系统热工水力学分析、系统故障树分析、人因可靠性分析、共因失效分析、编码系统、数据分析与评价、事故序列定量分析和分析结果及评价：简化的2级PSA工作任务包括导致堆芯熔化的主导事故序列分析、安全壳事件树和向环境释放的放射性源项。     

铀纯化转化设施始发事件分析

始发事件分析是概率安全分析的基础,对始发事件进行定量化评价是概率安全分析获得量化风险结果的必要条件。本文采用工程评估和演绎分析相结合的方法识别了典型铀纯化转化设施的始发事件,根据设施安全保护措施的异同将始发事件分为5组,并对铀纯化转化设施主要关注的UF₆泄漏事件采用事件树分析法进行事故序列分析,得到UF₆泄漏事件序列和相应的频率。     

CNP1500标准设计大LOCA事故的概率安全评价研究

本文通过用事件树，故障树方法量化了CNP-1500标准设计的堆芯损伤（损坏）频率，对核电站进行风险评价和平衡设计；描述了冷却剂丧失（LOCA）事故的概率分析。采用PSA分析程序Risk Spectrum，以热段大LOCA为例，用事件树方法对初因事件及其引起的系统响应进行事故序列分析，找出可能导致其堆芯熔化事故序列。从热段大LOCA计算结果来看，CNP1500 PSA的结果是可以接受的。     

CEFR放射性钠火风险分析

对CEFR的研究发现,一回路外的钠净化管道或阀门破裂将导致放射性钠火事故发生,其中309/1设备间的泄漏后果最严重。采用概率安全评价技术对该事故进行放射性风险分析,依据钠泄漏及钠火发生后相关系统的响应特性,确立了44个事故序列,建立了事件树-故障树模型。对模型进行定量分析     

核电厂仪控系统误动作事故分析

为全面评价核电厂仪控系统误动作事故,提出基于简化分析的方法,该方法基于功能组概念对仪控误动作假设始发事件（PIE）进行了系统化地识别和归并,得到不能被已有事故分析包络的潜在新增事故工况,并根据保守的分析假设和准则,针对识别出的潜在新增事故进行了定性评价和定量分析。研究结果表明,核电厂保护系统能够对仪控系统误动作事故提供多样化保护,事故后果满足验收准则,并建议增设“2个热管段实际压力与饱和压力之差低2信号触发安注启动以及所有主泵停运”功能。      

非能动压水堆核电厂地坑滤网堵塞风险影响模拟分析

采用Risk Spectrum 1.3版软件建立事件树模型,对小LOCA始发事件下的堆芯损伤事故序列进行校核计算研究,分析得出了地坑滤网堵塞对于我国大型先进压水堆安全的影响。结果表明,虽然我国大型先进压水堆对于地坑滤网在设计上进行了优化改进,但在小LOCA始发事件下发生地坑滤网堵塞对于电站安全的影响仍然很高,地坑滤网堵塞问题仍然不能忽视。     

基于二叉决策图的故障树求解法

探讨了二叉决策图(BDD)求解故障树失效概率和最小割集(MCS)的方法,包括如何将故障树转化为BDD、用BDD求解最小割集、利用零压缩二叉决策图(ZBDD)表示最小割集以减少存储空间、基于BDD求解故障树顶事件失效概率.用程序实现了BDD算法,以某电厂PSA模型部分分枝为对象,通过手工计算和RiskSpectrum P...     

适用于Living PSA快速求解最小割集的算法研究

Living PSA是现今核电厂安全分析的热点之一,核电厂本身是一个非常复杂的系统,其相应的Living PSA模型也相当庞大,这样在Living PSA的应用中,计算软件的分析速度成为限制其发展的瓶颈之一.本文基于现行常用的PSA分析算法,设计了一个能够快速求解故障树的算法.该算法首先将生成的故障树转化成用于计算的标准故障树,然后对标准故障树进行模块化,生成四类基本的独立子树,最后调用优化过的最小割集算法并采用多叉树方法进行割集的合并和吸收.该算法目前已应用于核电站快速风险分析软件平台NFRISK的开发中,并通过应用于中国实验快堆的一些系统和设备的故障树分析对其进行了初步验证.     

适用于动态概率安全评价的故障树逻辑简化方法

对故障树进行逻辑简化将有效提高分析计算的速度。根据故障树结构特点,提出了基于贪心算法的故障树逻辑简化方法。该方法已编程实现,并采用实际系统的故障树进行了测试。实践证明,该方法可大幅度提高分析求解速度,同时,该方法所采取的贪心策略又可运用在故障树分析的其他方面。     

ZBDD algorithm features for an efficient Probabilistic Safety Assessment

This paper explains a Zero-suppressed Binary Decision Diagram (ZBDD) algorithm and introduces advanced ZBDD algorithm-based features that are implemented into a fault tree solver Fault Tree Reliability Evaluation eXpert (FTREX). The ZBDD algorithm and its advanced features have been developed for solving a fault tree in Probabilistic Safety Assessment (PSA) of a nuclear power plant. The ZBDD can be interpreted as a factorized structure of minimal cut sets (MCSs). A ZBDD algorithm was developed in 2004 for performing a Boolean operation of ZBDDs. The ZBDD algorithm is based on a set of new ZBDD operation formulae. The ZBDD algorithm is known as an efficient replacement of a cutset-based algorithm that is based on traditional Boolean algebra.This paper explains how to perform a delete-term operation and a rule-based post-processing of MCSs by the ZBDD algorithm and demonstrates the efficiency of the ZBDD algorithm by performing benchmark tests. By using the ZBDD algorithm in this study, a long run time for (1) solving a fault tree, (2) performing a delete-term operation to handle negates, and (3) performing a rule-based post-processing of MCSs could be significantly reduced. Since the ZBDD algorithm is based on the factorized form of MCSs, it uses much less memory than the cutset-based algorithm.Due to the small memory requirement of the ZBDD algorithm from solving a fault tree to performing a rule-based post-processing, a much smaller truncation limit can be used than that in the cutset-based algorithm. By lowering the truncation limit, accurate PSA results such as a core damage frequency and importance measures could be calculated by the ZBDD algorithm.     

扩展割集矩阵在故障树快速求解方法中的应用

提出了扩展割集矩阵的概念及其展开规则．并将其应用在故障树快速求解方法中模块最小割集以及故障树最小割集的求解上．同时,利用矩阵形式．结合故障树求解的特点．提出了若干优化策略。     

FFTA: A fast fault tree analysis program

This paper presents a computer program for fault tree analysis. The algorithm is a bottom-up algorithm and the detailed procedure of the program is explained. The analyses are performed for six sample fault trees and the results are compared with those obtained by the BAM and CUT codes. This program has a ten to thousand times faster calculation speed compared with the BAM and CUT codes.     

Development of SUPKIT-II: Computer Aided Fault Tree Analysis System

A computer aided reliability analysis system, in which an interactive graphic terminal can be used, to construct, modify, analyze, and store fault trees is developed. The system, SUPKIT-n, a computer aided fault tree analysis system has functions for fault tree automated construction (PREP) and fault tree graphics (GRAPH). The former automatically generates a fault tree by a hierachical structure based on system configuration and specifications, and/or from failure information, while the latter indicates, modifies, and evaluates the fault tree through CAD/CAM terminals. Therefore, PREP decreases man-hours and mistake occurrences in constructing fault trees and GRAPH enables users to evaluate system reliability and to compare system design plans easily and quickly.     

适用于Living PSA的故障树求解方法

Living PSA是当前核电厂的安全分析与评价中最热点的问题之一，Living PSA实现中最为根本而又关键的问题是“速度”问题：在现有PSA方法的基础上，根据Living PSA的特性，设计了一种适用于Living PSA的故障树求解方法，即独立模块排序求解法，并通过例子详细地说明了该方法实现过程：这个方法除了能快速地求解故障树以外，当故障树结构或故障树中部件可靠性模型或数据发生变化时能实时地求解故障树。     

Fuzzy probability on reliability study of nuclear power plant probabilistic safety assessment: A review

Fault tree analysis (FTA) is a graphical model which has been widely used as a deductive tool for nuclear power plant (NPP) probabilistic safety assessment (PSA). The conventional one assumes that basic events of fault trees always have precise failure probabilities or failure rates. However, in real-world applications, this assumption is still arguable. For example, there is a case where an extremely hazardous accident has never happened or occurs infrequently. Therefore, reasonable historical failure data are unavailable or insufficient to be used for statistically estimating the reliability characteristics of their components. To deal with this problem, fuzzy probability approaches have been proposed and implemented. However, those existing approaches still have limitations, such as lack of fuzzy gate representations and incapability to generate probabilities greater than 1.0E-3. Therefore, a review on the current implementations of fuzzy probabilities in the NPP PSA is necessary. This study has categorized two types of fuzzy probability approaches, i.e. fuzzy based FTA and fuzzy hybrid FTA. This study also confirms that the fuzzy based FTA should be used when the uncertainties are the main focus of the FTA. Meanwhile, the fuzzy hybrid FTA should be used when the reliability of basic events of fault trees can only be expressed by qualitative linguistic terms rather than numerical values.