Developments in Leak-before-Break

A Leak-before-Break (LbB) argument is aimed at demonstrating that leakage of fluid through a crack in the wall of a pressure component can be detected prior to the crack reaching instability, at which time a sudden catastrophic failure could occur. Such arguments are used in many European and other countries when evaluating the safety and integrity of piping components in nuclear reactor systems, mainly as a defense in-depth scenario.

The development of a LbB assessment will usually involve some or all of the following to be considered:

• Crack shape development of a part-through-wall flaw as it grows in the through-wall direction by a sub-critical mechanisms such as fatigue
• How the flaw eventually breaks through the wall and recharacterises as a through-wall flaw
• Limiting size of through-wall flaw
• Crack opening area of through-wall flaws
• Leakage rate of fluid of through-wall flaws (from crack opening area information)
• Evaluation of detectable leakage flaw size (from leakage rate and flow detection methods)
•  Evaluation of margin between limiting through-wall size and detectable leakage flaw size

LbB therefore involves the linkage of fracture mechanics principles with fluid dynamics theory.

A substantial amount of research and development work on LbB aspects has continued to be undertaken in recent years. This has included the EU Horizon 2020 project, ATLAS+ whereby both deterministic and probabilistic LbB methodologies have been studied and progressed.

This two half-day free online event consists of presentations given by leading experts in the field of LbB followed by a general discussion on such aspects as further required developments in the field, a potential European roadmap for LbB, regulatory aspects, plant life extension and new build.

The programme is heavily centred, but not exclusively, on developments coming out of the ATLAS+ project.

Click to view the programme (timings are GMT).