THE EFFECT OF GRAIN SIZE ON IGSCC IN SS 316L IN SIMULATED BWR ENVIRONMENT

摘要

Disposition lines are used for flaw tolerance analysis, structural integrity assessment and life prediction of reactor components. One parameter normally not accounted for in the development of disposition lines is the grain size of the material. However, in actual reactor systems there can be variations in grain size within one component, as well as between different components. The objective of this project was therefore to study if the susceptibility to intergranular stress corrosion cracking (IGSCC) in one heat of Type 316L stainless steel is affected by the grain size.CGR measurements were conducted on sixteen 25 mm CT specimens in simulated BWR environments. Eight specimens were loaded by pull rods (active load), and the remaining specimens were bolt loaded. Three different grain sizes were studied on the same heat of material: 26, 347 and 590 μm.Intergranular cracking was observed in 13 out of 16 specimens. No obvious difference in crack growth rate (CGR) was observed between the three grain sizes. Further, a clear effect of hydrogen water chemistry (HWC) was observed in all material conditions, where the CGR was considerably lower in HWC compared to normal water chemistry (NWC).