Recent Applications of ASME Code Case N-513 for Evaluation of Nonplanar Leaking Flaws

ASME Code Case N-513, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping, provides evaluation rules for the temporary acceptance of flaws, including through-wall flaws, in moderate energy Class 2 or 3 piping without performing repair/replacement activities. The Code Case has gone through three revisions with the latest approved by ASME Section XI being N-513-2. The Code Case allows for evaluation of both planar and nonplanar flaws. The planar flaw evaluation uses the rules in Appendix C of ASME Section XI. The nonplanar flaw evaluation uses the procedure provided in Code Case N-480. This Code Case has been used widely in the nuclear industry ever since it was published. Its use is expected to grow with plant aging and especially since Revision 2 was recently endorsed by the NRC in Regulatory Guide 1.147 without condition. The paper describes three specific applications of the Code Case to accept leaking flaws in piping components for continued operation till the end of the operating cycle when repairs could be performed. The use of this Code Case thus avoided costly and unnecessary shutdown of the plants in these cases. The evaluation procedures using this Code Case for these instances are described in the paper.