IASCC crack initiation testing of thimble tube material with a dose up to 80 dpa under PWR conditions

IASCC (Irradiation Assisted Stress Corrosion Cracking) crack initiation tests have been carried out on thimble tube material retrieved from a Belgian PWR. The crack initiation tests were carried out by constant load testing of thimble tube specimens at different stress levels. The time-to-failure was determined as a function of the applied stress to find a stress limit under which no stress corrosion cracking will take place. The thimble tube was made of 316L cold-worked stainless steel and the dose profile along the thimble tube ranges from 45 to 80 dpa. This allows adding crack initiation data for dpa values that have not been significantly reported i.e. in the range of 45-55 dpa and at 80 dpa. The results can be used to determine whether the critical stress limit under which no IASCC occurs saturates for a dpa value larger than 30 dpa or whether a small further decrease with dpa can be observed.