Abstract Over the recent decades, there has been a growing interest in nuclear power plants to develop maintenance activities in the form of risk-based models. Maintenance planning plays a key role in the probabilistic safety assessment (PSA) applications. The importance of these activities, especially with considering the effects of component degradation, is quite clear in term of compromising between conflicting objectives such as achieving the highest level of availability while minimizing the costs of implementing these activities. Given the limitations of applying current PSA techniques to complex maintenance policies, and also the difficulty in modeling the effects of component maintenance strategies and degradation using fault tree (FT) analysis; in this paper a multi-state continuous-time Markov method is presented to model three test and repair policies (T&R) for components with focus on changing technical specification (TS) such as surveillance test intervals (STIs). First, Markov models are developed for three different test policies taking into account the effects of degradation. Then, these models are applied for analyzing the availability of critical components of emergency core cooling system (ECCS) of the VVER-1000/V446 nuclear power plant (NPP) as a case study. In Policy 1, no additional test on the other components is performed. The test procedure is performed according to the plan test as originally scheduled. In Policy 2, an additional test is performed after the failed component is repaired and in Policy 3, an additional test is carried out promptly on the other redundant components after the first failure detection.

中文翻译：

---

监视测试下具有老化效应的安全系统冗余部件多状态不可用性分析

摘要 近几十年来，人们对核电厂以基于风险模型的形式开展维护活动越来越感兴趣。维护计划在概率安全评估 (PSA) 应用中起着关键作用。这些活动的重要性，特别是在考虑组件退化的影响时，在相互冲突的目标之间进行妥协是非常明显的，例如实现最高级别的可用性，同时最小化实施这些活动的成本。鉴于将当前 PSA 技术应用于复杂维护策略的局限性，以及使用故障树 (FT) 分析对组件维护策略和退化的影响进行建模的难度；在本文中，提出了一种多状态连续时间马尔可夫方法来为组件建模三个测试和修复策略 (T&R)，重点是不断变化的技术规范 (TS)，例如监视测试间隔 (STI)。首先，考虑到退化的影响，为三种不同的测试策略开发了马尔可夫模型。然后，将这些模型应用于分析 VVER-1000/V446 核电站 (NPP) 应急堆芯冷却系统 (ECCS) 关键部件的可用性作为案例研究。在策略 1 中，不对其他组件执行额外测试。测试程序按照原定的计划测试执行。在策略 2 中，在修复故障组件后执行附加测试，在策略 3 中，