Mechanisms of Metal Degradation in Equipment and Pipelines of Turbo Plants of Nuclear Power Plant Units: Classification and Identification

Operation of nuclear power plant units is accompanied by the development of various metal degradation mechanisms (MDM) under the influence of the working environment. Prevention of damage and elimination of sudden destruction of equipment and pipelines (E&P) at operating nuclear power plants depends on the timely identification of those elements and units in which the preconditions for the manifestation and intensification of metal degradation mechanisms are created. In this case, the search for the causes of damage to pipeline lines and equipment parts should be based on the determination of the dominant MDM. The effectiveness of the technical measures being developed to restore and prevent similar damage in the future depends on the correct solution to these problems. Despite significant experience and accumulated statistical data on damage to the metal of the working contours of nuclear power plant units, the establishment of identification features and the detection of dominant MDM in the operating conditions of turbine installations of nuclear power plant units remain highly relevant. This is confirmed by the existing differences in approaches to the classification of MDM and the lack of a clear methodology for their identification when detecting defects and analyzing cases of damage to pipeline elements and equipment. Due to the complexity of the physical and chemical processes and patterns of MDM, their deep and fairly large-scale study is required; therefore, as a rule, the study of a specific MDM is carried out by separate specialized scientific organizations and institutes. This circumstance makes it difficult to form a unified approach to their systematization and classification in order to obtain a complete picture of the dominant mechanisms of damage to E&P turbine installations of nuclear power plant units. At the same time, the achievements of recent years in this area make it possible to formulate more advanced criteria and recommendations for classification and identification of MDM, which are advisable to use in practice, including in the development of industry guidance documentation on this topic.