Reliability assessment of nuclear reactor heat transfer tubes under stress corrosion degradation and shocks based on the Markov renewal process

The reliability of nuclear reactor steam generator heat transfer tubes subjected to stress corrosion and shock damage has emerged as a critical area of focus in reactor structural safety research. This study develops a reliability analysis model that incorporates the bidirectional interaction mechanism between degradation and shock damage, formulated within the framework of the Markov renewal process. State-dependent equivalent stress level parameters are introduced to quantify this interaction mechanism. For the cumulative shock failure mode, a numerical analysis method based on the Laplace transform is proposed, with its accuracy validated through Monte Carlo simulation. Case study findings demonstrate that incorporating the damage interaction mechanism yields a more conservative reliability assessment of heat transfer tubes compared to assessments that omit this mechanism. The outcomes of this research provide theoretical guidance for the integrity evaluation of critical nuclear reactor structures, prediction of remaining service life, and formulation of operation and maintenance strategies.