Development of criteria for protection against pipe breaks in LWR plants

A proving test for the structural integrity of safety-related carbon steel piping components in light water reactor plants was conducted in NUPEC as a four-year project, in which the applicability of the Leak-Before-Break (LBB) concept to protect against a postulated pipe break was reviewed in parallel with the clarification of fracture behavior. The comprehensive review of LBB applications consists of applicable piping systems, premise for evaluations, procedure and evaluation findings. The review concluded that present practice for design, fabrication, installation and operation can ensure structural integrity and moreover postulated that instantaneous pipe break as a basis for structural design is unrealistic if certain conditions are met. Fatigue is the only failure mechanism to be considered to affect the piping system.