Session: MF-12-01 Leak Before Break

Paper Number: 125301

125301 - Effect of Pipe Restraint on Crack Opening Displacement for Leak-Before Break Analysis 

In nuclear power plants, Leak-before-break (LBB) is a widely recognized methodology for assessing structural integrity of pressure vessels and pipes. The LBB concept is based on the analysis, demonstrated by deterministic fracture mechanics evaluation, that a through-wall crack can be safely and in a timely manner detected by the available leak detection systems and does not challenge the pipe's capability to withstand any design loading before a catastrophic break occurs. In this process, crack opening displacement (COD) is a vital component for evaluating the leak rate for a given through-wall crack. Typical approach is the use of analytical COD solution derived for idealized straight pipes without restraints. However, restraint free analytical solution overestimates the COD and the leak rates when compared to end-restraint pipes, which represent an actual nuclear power plant piping layout. This yields in non-conservative results. Conservatively, the applied moment at crack section can be overestimated (not analyzed in this paper).

In this paper, results from 3-D finite element analysis simulating the COD are presented for piping system subjected to pressure and moment loading with end-restraint. Both elastic and elastic-behavior of the pipe are considered. The analysis is performed for various circumferential through-wall crack angles and restraint length. These results are also compared against analytical model in estimating the reduction in COD due to end-restraint. This work was performed as part LBB Benchmark II program conducted by Nuclear Energy Agency (NEA), Metal subgroup.

Presenting Author: Deepak Somasundaram Candu Energy Inc

Presenting Author Biography: Deepak Somasundaram is a Senior Engineer with wide range of experience in various sectors including Nuclear, Oil & Gas, Aerospace and Defense in Design, Finite Element Analysis (FEA), fracture mechanics and probabilistic applications.

Authors:

Deepak Somasundaram Candu Energy Inc
Xinjian Duan Candu Energy Inc
Daniel Leary Candu Energy Inc
Min Wang Candu Energy Inc