Deterministic and Probabilistic Evaluations for Uncertainty in Pipe Fracture Parameters in Leak-Before-Break and In-Service Flaw Evaluations

摘要

The report presents new results from deterministic and probabilistic analyses to evaluate the significant of a number of technical aspects that may affect LBB or in-service flaw evaluations. In most cases there are both deterministic and probabilistic results. The deterministic analyses were conducted independently of the probabilistic analyses, which offered the opportunity to validate conclusions from each of these independent studies. The technical aspects evaluated relative to LBB uncertainties were: (1) Evaluation of different crack morphology default values, (2) evaluation of COD dependent and independent crack morphology models for tight crack leak-rate analyses, (3) changes of normal operating and N+SSE stress levels on conditional failure probability, (4) dynamic and cyclic loads history effects on load-carrying capacity of through-wall-cracked pipe, (5) evaluation of the effect of off-centered cracks, (6) evaluation of the effect of restraint of pressure induced bending, and (7) evaluation of the effect of residual stresses on leak-rate analyses. Uncertainty analyses conducted relative to in-service flaw evaluations were: (1) dynamic and cyclic load history effects on load-carrying capacity of surface-cracked pipe, and (2) effect of uncertainty in UT flaw sizing. The relative ranking of importance is given for the significance of each technical aspect investigated.