Preservice and inservice requirements for containment structures - a status report

Preservice and inservice requirements for Class MC containment structures are contained in Subsection IWE, Requirements for Class MC Components of Light-Water Cooled Power Plants, of Section XI. Rules for Inservice Inspection of Nuclear Power Plant Components, of the ASME Boiler and Pressure Vessel Code. Rules for the preservice examination, inservice inspection, repair, modification, replacement and system pressure tests for Class MC (metal) containments and steel portions of Class CC (concrete) containments not backed up by concrete and their integral attachments in PWR and BWR light-water cooled nuclear power plants are included. Rules for Class CC containments are currently being developed and will be published in Subsection IWL, Requirements for Class CC Components of Light-Water Cooled Power Plants. First published in the Winter, 1981 Addenda to Section XI, Subsection IWE has been adopted by a number of state jurisdictions and is presently being reviewed by the Nuclear Regulatory Commission for adoption in Title 10. Part 50 of the Code of Federal Regulations (10CFR50). In the interim, ASME Nuclear Code Case N-236, Repair and Replacement of Class MC Vessels, may be used for the preservice examination, repair welding, acceptance standards, system pressure tests, and replacements for metal containment structures. When approved, the requirements in Subsection IWE and Subsection IWL will provide a reasonable and systematic basis for assuring the integrity of a containment vessel during its service lifetime and will require mandatory compliance by plant owners. This paper provides an overview of these requirements with emphasis on the practical considerations that should accompany user compliance