Technical Basis for Proposed Revisions to ASME Code Case N-513 and Some Applications to Moderate Energy Piping

Code Case N-513 provides evaluation rules and criteria for temporary acceptance of flaws, including through-wall flaws, in moderate energy piping. The application of the Code Case is restricted to Class 2 and 3 systems, so that safety issues regarding short-term system operation are minimized. The first version of the Code Case was published in 2000. Since then, there have been two revisions to the Code Case (N-513-1 [1] and N-513-2 [2]) that have been published by ASME. There is currently work underway to incorporate additional changes to the Code Case to make it easier to apply to through-wall, nonplanar flaws. The technical basis for the original version of the Code Case and the first revision, N-513-1, has been previously published [3]. This paper provides the technical basis for the changes in the second revision of the Code Case, N-513-2, and the proposed changes to a third revision. These changes specifically address exceptions taken by the NRC in the first version of the Code Case and more importantly provide flaw evaluation rules for through-wall, nonplanar flaws. The flaw evaluation rules for through-wall, nonplanar flaws are based on ASME Code Section III branch reinforcement rules and also a quasi planar flaw approach. These developments are described in the paper. In addition, practical examples involving the application of the Code Case to through-wall, nonplanar flaws are also provided.Copyright © 2006 by ASME