By: Jennifer Correa
Subsequent License Renewal (SLR) will require a shift in the approach for managing plant components for thermal fatigue. The components are older and will have experienced more fatigue damage. As time goes on, more components will become fatigue-challenged, meaning that they will require more management to demonstrate serviceability.
There are several approaches that can be taken to manage fatigue-challenged components in SLR.
Refining the design fatigue analyses is one approach that has been widely used in License Renewal (LR), and will remain useful in SLR. Components that were previously managed through cycle counting alone may still be managed through cycle counting if a refined analysis results in fatigue and environmentally-assisted fatigue (EAF) cumulative fatigue usage values below 1.0.
Another useful approach is to revisit assumptions made about plant operation earlier in life. Conservative assumptions were made about early plant operation for many components. This was often done for expediency and may have been sufficient for LR, but as the components age, those assumptions may prove too conservative. Revisiting these assumptions can help lower the overall fatigue usage for components.