Abstract :
In January 1994, the US Nuclear Regulatory Commission (NRC) issued a proposed rule-making to adopt Subsections IWE and IWL of Section XI of the ASME Boiler and Pressure Vessel Code into Title 10, Part 50, paragraph 50.55a of the Code of Federal Regulations. Subsection IWE contains requirements for Class MC (metal) containments and metallic liners of Class CC (concrete) containments. Corresponding requirements for concrete and post-tensioning systems for Class CC containments are in Subsection IWL. Together with the general requirements in Subsection IWA of Section XI, these requirements form a comprehensive basis for the preservice examination, inservice inspection, modification, repair, replacement and pressure testing for all steel and concrete containments and metallic containment liners. Mandatory compliance with Subsections IWE and IWL will be required by all nuclear utilities in the USA on final approval of the rule-making by the NRC. This paper describes the regulatory basis for containment inservice inspection in the USA, together with a description of the requirements in Subsections IWE and IWL. The paper also includes a brief history of the development of these rules by the ASME code committees, and a discussion of containment aging and degradation mechanisms. The experience base that fostered todayʹs containment inspection philosophy is also presented. The period for public review and comment of the NRCʹs proposed rule-making in 10CFR50.55a closed on 25 April 1994. Although many positive comments were received, numerous objections were raised that the ASME code requirements for containment inservice inspection are impractical or unnecessary. This paper includes an assessment of the comments submitted to the NRC. Arguments both for and against adoption of the rules were being reviewed by the NRC during the summer and autumn of 1994. Hence, the question remains: containment inservice inspection: where do we go from here?
