Lifetime integrity requirements for containments in the United States

Abstract

Assuring the lifetime integrity of containment structures for nuclear power plants is becoming increasingly important as existing design criteria are reexamined, as new requirements for containment inspection and testing are formulated, and as today's operating plants grow older. Regulatory requirements for containments in the United States are contained in the Code of Federal Regulations and in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. New requirements for the preservice examination and inservice inspection of Class MC (metal) containments have been published in Section XI, Subsection IWE, of the ASME Boiler and Pressure Vessel Code. Requirements for Class CC (concrete) containments have been published in Subsection IWL. Federal regulations that will require mandatory compliance with the ASME Code by nuclear plant owners in the United States are forthcoming. Parameters for extending the life of current United States nuclear plants beyond the 40 year design lifetime are presently being formulated. Two pilot plant life extension (PLEX) studies, one for a BWR and one for a PWR, serve as models for extending the life of today's aging plants. This paper presents an overview of the regulatory requirements for containments in the United States and the new preservice examination, inservice inspection and related requirements for Class MC and Class CC containments in the ASME Boiler and Pressure Vessel Code. Operational and life extension considerations for containment structures, including the findings from pilot studies of typical PWR and BWR containments, are also discussed. Together, the regulatory and Code requirements and recommendations from the plant life extension studies provide a basis for improved lifetime integrity for containments in the United States.