The US light water reactor (LWR) fleet is a strategic US asset for meeting the demand for clean, sustained, and affordable energy. Extended operations are governed by endogenous (e.g., aging management, operation costs) and exogenous (e.g., natural gas, deployment of advanced nuclear reactors) economic factors but also by technical issues associated with doubling the original 40 year license period. Materials aging includes all critical components of the reactors, such as internals, reactor pressure vessel, cabling, and concrete structures.