In pressurized water reactor plants, the degradation of steam generator tubes has been one of the main economic and safety problems. Steam generator tubes are subjected to the degradation mechanism of stress corrosion cracking, in which an unstable crack growth may lead to their structural failure. In general, deterministic criteria provide the least conservative assessment in order to plug or sleeve the cracked tubes. As the crack growth rate under stress corrosion cracking is of high random nature, the structural integrity assessment of steam generator tubes must be performed taking into account the failure probability at current and next inspections. In this paper, a stochastic model is applied for performing the operational assessment of steam generator tubes for any time interval. The results obtained with this model are compared with others, such as Monte-Carlo simulation and non-evolutionary statistical model. The proposed methodology is able to provide efficiently a less conservative failure probability. The plausibility of stochastic models in the structural integrity assessment of steam generator tubes is reached in favor of their operational life extension.

在压水反应堆工厂中，蒸汽发生器管的退化一直是主要的经济和安全问题之一。蒸汽发生器管受到应力腐蚀开裂的退化机制，其中不稳定的裂纹扩展可能导致其结构失效。通常，确定性标准提供了最不保守的评估，以便堵塞或套上破裂的管子。由于应力腐蚀开裂下的裂纹扩展速率具有高度随机性，蒸汽发生器管的结构完整性评估必须考虑到当前和下次检查的失效概率。在本文中，随机模型应用于执行任何时间间隔的蒸汽发生器管的运行评估。用这个模型得到的结果与其他模型进行了比较，例如蒙特卡罗模拟和非进化统计模型。所提出的方法能够有效地提供较不保守的故障概率。随机模型在蒸汽发生器管结构完整性评估中的合理性达到有利于延长其使用寿命。