Abstract
This paper presents a leakage prediction study for Leak Before Break (LBB) assessments. The LBB concept has emerged as an essential tool for ensuring the safety of nuclear installations and pressurized piping systems. The approach is backed by accurate estimation of leakage rates from postulated cracks. In this study the methodology is based on the UK procedure for assessing structures containing defects (R6). The research is part of the ongoing in-house development of a software for LBB analyses and it aims to better understand and improve leak rate prediction methodologies for LBB assessments. The software is comprised of structural integrity modules and thermal hydraulic modules. This study presents the implementations of different coolant leak rates flow models, the Henry-Fauske model for flashing subcooled fluids and as single-phase Bernoulli model for lower temperatures. The thermal-hydraulics Henry Fauske model is evaluated against available experimental data and the differences are discussed. The Bernoulli based model is compared with another software. The implemented procedure is compared with two different software results for the structural modules. The structural calculations show coherence between the implemented procedure and the benchmark software that is based on the same methodology. In contrast the results are considerably different respect to another available software. The data show the significance and limitations of each model in various cases.
