Influence of surface defects on the working performance of mechanical seals for nuclear reactor coolant pumps

Nuclear reactor coolant pumps require frequent maintenance to ensure operational safety. One critical aspect of this maintenance is verifying the integrity of the mechanical sealing system. Due to the lack of an evaluation criteria and an incomplete understanding of how end-face defects lead to failure, defective mechanical seals are often replaced empirically, which not only contributes to economic losses but also poses risks to reactor safety. To reveal the mechanism by which surface defects affect sealing performance, this study proposes a classification method for end-face defects based on the analysis of approximately one hundred used mechanical seals. A defect characterization model was established by extracting key features of the observed defects. The influence of these defects on sealing performance was analyzed using a liquid-thermal-solid coupling model. Changes in sealing gap, leakage rates, and film stiffness with respect to defect size, location, and other characteristics are discussed. This work contributes to a deeper understanding of defect failure mechanisms. These results can serve as a reference for evaluating defective seals.