Inspection of Containment Structures in the U.S.A.

摘要

In the United States, until 1996, the containment structure visual inspections were performed as part of the containment integrated leak rate testing in accordance with Appendix J of 10 CFR Part 50, "Primary Reactor Containment Leakage Testing for Water-Cooled Power Reactors". In August 1996, the U.S. Nuclear Regulatory Commission amended its regulation, 10 CFR 50.55a, "Codes and Standards," to incorporate by reference Subsections IWE and IWL of Section XI of the ASME Boiler and Pressure Vessel Code for inspection of containment structures in light-water-cooled nuclear power plants. Subsection IWE provides the requirements for inservice inspection, repair, and replacement of Class M C pressure-retaining components (i.e., steel containments) and their integral attachments, and metallic shell and penetration liners of Class CC pressure-retaining components (i.e., concrete containments) and their integral attachments. Subsection IWL provides the requirements for preservice examination, inservice inspection, and repair of the reinforced concrete and post-tensioning systems of Class CC components. The regulation endorsed the requirements of the 1992 Edition and 1992 Addenda of Subsections IWE and IWL with a few supplementary requirements for inspection of steel and concrete containments. A later amendment to the regulation also endorsed the use of the 1995 Edition and the 1996 Addenda of Subsections IWE and IWL with a consistent set of supplementary requirements. The regulation requires the owners of nuclear power plants to complete the first period inspections of their containments by September 9, 2001. This paper discusses (1) instances of containment degradation found before 1996, as a result of visual examinations and ad hoc findings, (2) the need for periodic inservice inspections, and (3) issues raised during the implementation of the regulatory requirements.