动态故障树在主蒸汽管道破裂事故风险评价中的初步应用研究

冗余设计使核电厂系统广泛存在复杂时序失效行为，而基于静态故障树(Static fault tree, SFT)的事故风险评价无法对时序失效行为进行准确模拟。为解决这一问题，本工作提出一种基于事件树+动态故障树(Dynamic Fault Tree, DFT)的事故风险分析框架，并以典型三代压水堆主蒸汽管道破裂事故为例，开展动态事故风险案例分析。首先，建立主蒸汽管道破裂事故的事件树模型以及相关系统的DFT模型；其次，将系统故障树分为DFT模块和SFT模块，并将DFT树模块替换为超级事件参与后续计算；最后，采用割集法计算案例结果，并在相同条件下与传统SFT方法进行对比。案例分析结果表明:(1) 相较于SFT方法，所提方法更为贴近系统的真实失效场景；(2) 针对文中案例所提方法可以降低相关系统失效概率与部分事故序列的发生频率、有助于释放保守风险。

Application of Dynamic Fault Tree in Risk Assessment of Main Steam Line Break Accident

The systems in nuclear power plants have complex sequence failure behaviors due to redundant design, and the traditional static fault tree(SFT) in risk assessment cannot accurately simulate the sequential failure behaviors of the systems in nuclear power plants. In this paper, an accident risk analysis framework based on event tree+Dynamic Fault Tree(DFT) is proposed to solve this problem, and the main steam line break(SLB) accident is used as an example to carry out the analysis. First, an event tree model of the SLB accident and the DFT model of the related system are established; Then, the system fault tree is divided into DFT modules and SFT modules, and the result of the DFT modules are replaced with super events to participate in subsequent calculations; Finally, the cut set method is adopted to calculate and analyze SLB accident risk, and results are compared with the traditional SFT method under the same conditions. The results show that (1) Compared with the SFT method, the result calculated by the proposed method is closer to the real system failure scenario, and the conservativeness of the result is relaxed; (2) The proposed method can accurately simulate the SLB accident, which is beneficial for operational risk management and maintenance optimization in the future.