Failure Analysis and Countermeasure Research for Drain Pipelines of Nuclear Power Plant Conventional Island

Multiple weld failures and leakages have occurred on the drain pipelines within the conventional island of a domestic nuclear power plant, posing a threat to the safe and stable operation of power units. In this study, a comprehensive failure analysis was performed using chemical composition analysis, metallographic examination, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and numerical simulation. The results indicate that the primary cause of weld cracking is fatigue failure induced by cyclic load impacts generated from the frequent on–off actuation of inverted-bucket steam traps. Based on the failure mechanism identified, corresponding control measures and optimization proposals are put forward for the drain pipeline system in the conventional island.