Containment structures of nuclear power plants

Nuclear power plants are energy-generating facilities that constitute one of the most important components of urban infrastructure. The containment structures of a nuclear power plant surround the reactor systems and serve as the final barrier preventing the release of radioactive materials. Given these critical functions, containment structures are constructed with prestressed concrete using highly durable materials, and their inner surfaces are sealed with liner plates fabricated from ductile steel. Moreover, the investigation and management of structural integrity of these complex structures are essential for ensuring public safety. Many engineers therefore devote significant effort to predicting the behavior of containment structures under potential hazard scenarios, among which fragility analysis is one of the most widely used assessment tools.

Fragility analysis

Fragility analysis measures the vulnerability of a structure when subjected to external or internal hazards such as earthquake, fire, or core damage events. One of the most important aspects of fragility analysis is the consideration of uncertainties in both load-carrying capacity and structural responses. Recent developments in fragility analysis have focused on reducing these uncertainties or incorporating them more comprehensively through advanced analytical techniques.
Pressure fragility analysis, in particular, can be improved by addressing current technological limitations. In existing frameworks, allowable strain limits are typically used as failure criteria, and actual leakage behavior is only indirectly considered. Moreover, these frameworks often do not explicitly account for uncertainties in input parameters that may influence structural capacity. To overcome this limitations, this study evaluates actual leakage behavior by estimating the number and width of cracks based on the stresses and strains in the concrete and liner plates. Furthermore, uncertainties in various input parameters will be incorporated in pressure fragility analysis and leakage estimation to identify dominant parameters affecting pressure capacity.