The concept of leak before break implies that any crack or defect which develops in a component will grow to a through-wall configuration, and can be detectable by plant monitoring systems before reaching a size that significantly reduce margins to component rupture. It is widely used in structural integrity design of pressurized components and vessels. LBB analyses are based on advanced fracture mechanics techniques. It is used as part of overall safety assessments for leaving real or postulated flaws in service for some operating period.