Inspection of nuclear power plant containment structures

Safety-related nuclear power plant (NPP) structures are designed to withsta nd loadings from a number of low-probability external and interval events, such as earthquakes, tornadoes, and loss-of-coolant accidents. Loadings inc urred during normal plant operation, therefore, generally are not significa nt enough to cause appreciable degradation. However, these structures are s usceptible to aging by various processes depending on the operating environ ment and service conditions. The effects of these processes may accumulate within these structures over time to cause failure under design conditions, or lead to repair. Steel and concrete containment structures in nuclear po wer plants are described and their potential degradation factors identified . Reported incidences of containment degradation are summarized. Current re gulatory in-service inspection requirements are reviewed. Nondestructive ex amination techniques commonly used to inspect NPP steel and concrete struct ures to identify and quantify the amount of damage present are described, a nd their capabilities and limitations identified. Finally, areas where nond estructive evaluation techniques require development (i.e. inaccessible por tions of the containment pressure boundary, and thick heavily reinforced co ncrete sections) are identified and prior research addressing these needed developments summarized. (C) 1999 Elsevier Science S.A. All rights reserved .