Session: DA-08-02 FFS Involving Piping and Pipelines

Paper Number: 105920

105920 - Probabilistic Leak Before Break 

The Double Ended Guillotine Break (DEGB) is a pipe failure mode in nuclear power plant installations that is the postulated root cause of a Loss Of Coolant Accident (LOCA). Pipe whip restraints and jet impingement shields are safety systems that mitigate the effects of this postulated accident. The Leak Before Break (LBB) failure mode occurs when a small leak from a cracked pipe is detected prior to the DBEG failure. The application of this failure mode and the detection of cracked pipes would increase defense in depth and justify the removal from the plant of the pipe whip restraints and the jet impingement shield, decreasing costs and maintenance time. In this study a probabilistic assessment is performed with an in-house developed LBB software. The assessment incorporates the complexity of the physical model and the diversity of the systems with stochastic input variables for the geometry, loads, material properties and crack parameters. The developed deterministic code is based on the UK procedure for assessing the integrity of structures containing defects (R6). The Detectable Leak Before Break (DLBB) procedure is used, which is based on the Failure Assessment Diagram (FAD) Option 1 assessment procedure. The structural integrity assessment is then coupled with the Henry-Fauske two-phase critical flow model for the evaluation of the Leakage Rate (LR). A sensitivity analysis is performed in order to reduce the number of probabilistic variables. The output from the assessment is the probability of defect detection prior to structural failure. The Monte Carlo method is the probabilistic method used. The probabilistic results are then compared with the safety factors currently used for deterministic LBB assessments.

Presenting Author: Francesco Brigante NRG

Presenting Author Biography: Francesco in 2020 got his Master of Science in Nuclear Engineering at the University of Pisa (Italy) after a Bachelor of Science in Aerospace Engineering. Since 3 years he is a consultant in the Asset Integrity Team of the Nuclear Research and Consultancy Group in Petten, The Netherlands.

Authors:

Francesco Brigante NRG
Fabio Pasti NRG
F. H. E. De Haan - De Wilde NRG