Irradiation creep and IASCC prediction method of PWR's core internal

—Verification of "Inspection and Evaluation Guideline for Reactor Internals of PWR(Baffle Former Bolt)"—

Abstract

PWR's core internals have aging due to IASCC (Irradiation Assisted Stress Corrosion Cracking). Although stress influences the occurrence of IASCC greatly, we have little data about PWR's irradiation creep which reduces stress. In this report, we assessed irradiation creep by using the removal torque of the baffle former bolts at the time of replacement. Then, we concluded that irradiation creep in PWR is approximately 50% of the irradiation creep in the fast breeder reactor. Moreover, we used this result to check the method for IASCC prediction method proposed in the last report which is applicable also to barrel former bolt and weld metal of barrel, and we confirmed the applicability of the IASCC prediction method for the actual plant.