Session: MF-12-01 Leak Before Break

Paper Number: 130937

130937 - Piping End Restraint and Leak-Before-Break Analysis 

The Working Group for the Integrity and Aging of Components and Structures (WGIAGE), a working group under the Committee for the Safety of Nuclear Installation (CSNI), is conducting leak-before-break (LBB) benchmark activities. The current benchmark activity consists of three topics and has 16 participating organizations representing 11 counties. One advanced LBB topic in this benchmark is evaluating the effects of end restraint and piping compliance (ERPC) on LBB acceptability. While a classical LBB evaluation typically considers piping ends that are free to both rotate and displace, prior work has demonstrated that the critical crack size and leakage crack size for restrained-end conditions can be substantially different than for free-end conditions. These differences can significantly affect LBB acceptability.
The ERPC benchmark topic compares identical piping systems where the end-restraint conditions vary, from both ends free to both ends fixed, as well as the distance of the flaw to the restrained ends. Prior analytical work from Kim et al. (2018) and and finite element work from Miura et al., (2001) along with estimates of cracked section rotation from Brust et al., (1994) have been employed in an iterative solution for simultaneous convergence of leak rate (crack opening displacement) and crack stability predictions. Sensitivity analyses have been performed to assess the effect of total pipe length, pipe diameter, and wall thickness (i.e., pipe compliance), and the distance of the analyzed flaw to the end restraints. Crack tip plasticity effects have also been considered. Guidance has been developed for making engineering assessments of these effects and where free-end assumptions may be appropriate.

Presenting Author: Robert Tregoning US Nuclear Regulatory Commission

Presenting Author Biography: Rob is the Senior Technical Advisor for Materials Engineering in the Office of Nuclear Regulatory Research at the NRC.

Rob is currently working on several projects within the Division of Engineering including research associated with advanced manufacturing techniques, degradation of reactor vessel internals, reactor pressure vessel embrittlement, high-energy line break, environmentally assisted fatigue, primary water stress corrosion cracking in Ni-based alloys, probabilistic and deterministic structural integrity assessment, and advanced non-light water reactor material issues.

Rob has previously supported the resolution of issues related to GSI-191, aging evaluations of cast austenitic steels, the development of loss-of-coolant-accident frequencies, and the structural integrity assessment of the degraded Davis-Besse reactor pressure vessel head.

Before joining the NRC, Rob worked for the U.S. Navy as a materials engineer at the Naval Surface Warfare Center (NSWC).

Rob received a B.S. degree in Mechanical Engineering from the University of Maryland, and M.S. and Ph.D. degrees in Mechanical Engineering from Johns Hopkins University.

Authors:

Robert Tregoning US Nuclear Regulatory Commission
Jay Wallace U.S. Nuclear Regulatory Commission