Structural assessments are an important part of NPP management programmes (e.g. ageing management, maintenance & design changes) and are required for effective periodic safety reviews. The aspects considered in TA4 include the definition of integrity assessment over the whole life cycle, the various degradation mechanisms, ageing issues, safety margins and harmonisation issues.
The Structures, Systems and Components (SSC) that need to be considered are those important for safety and availability, those that require high costs to replace and those that cannot be replaced without a significant long term refurbishment programme. Components like Instrumentation and Control (I&C) which are of high safety significance also need to be addressed.