Assessment of leak-tightness for nuclear reactor containment under overpressure conditions considering aging effects

Abstract

This paper assesses the aging effects on the leak-tightness of containment under overpressure conditions. A global containment model and the detailed sub-models for the three main penetration regions in the containment are established. The main aging forms and mechanisms of containment are clarified, and corresponding simulation schemes are provided. Through numerical simulation, the impacts of different aging forms on the failure pressure of containment are discussed from a deterministic perspective. Finally, the fragility and functional failure probability of containment under different aging conditions are evaluated. When 60 years of concrete degradation and prestress loss are considered, the pressure capacities of equipment hatch, personnel airlock, and pipe penetration are reduced by approximately 5%. Upon further considering steel liner corrosion, when the corrosion degree reaches 30%, the pressure capacities of these regions are reduced by 24.37%, 25.52%, and 22.83%, respectively. Within the scope of this study, the impact of steel liner corrosion on the risk of containment leakage is the most pronounced, whereas the impact of concrete degradation is minimal. If steel liner corrosion occurs simultaneously in three penetration regions, the whole containment will fail to meet the probabilistic performance goal when the corrosion degree reaches 30%.