Analysis of Ductile Crack Extension in BWR Feedwater Nozzles

摘要

The stability of ductile crack extension in very deeply cracked BWR feedwater nozzles is examined through analysis of a conservatively idealized two-dimensional elastic-plastic model. The assumed crack length to nozzle thickness ratio was varied from 0.5 to 0.95 and bilinear stress-strain relationships were used. The results indicate that the crack growth is J-controlled and Paris' stability criterion predicts stable crack growth up to approximately 2350 psi internal pressure for ASTM A508 and A533B pressure vessel steels even when the crack length to nozzle thickness ratio is 0.95.