Structural integrity assessment for internal crack in RPV shell

When quasi-laminar defects are detected in the RPV shell, these defects are modeled to single circular crack with a diameter of 2α and an angle of β from RPV wall enveloping these micro-defects like as the model used in the structural integrity assessment for Doel-3. An acceptable crack size is investigated for fracture assessment and initial crack size considering the fatigue crack growth by 60 years operation due to the JSME Fitness-for-Service (FFS) code. It was found that the initial crack with 2α of 4% smaller than the acceptance crack for fracture at the same location is accepted to exist. Although some discrepancies between Appendices E-1 and E-5 of the JSME FFS code exist for the treatment of internal crack, the structural integrity assessment can be performed for internal crack with some conservative assumptions. (author)