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There are approximately 440 operating reactors in the global nuclear power plant (NPP) fleet that have an average age greater than 20 years and design lives of 30 or 40 years. The United States is currently implementing license extensions of 20 years on many plants, and consideration is now being given to the concept of ldquolife-beyond-60,rdquo a further period of license extension from 60 to 80 years and potentially longer. In almost all countries with NPPs, authorities are looking at some form of license renewal program. There is a growing urgency as a number of plants face either approvals for license renewal or shut down, which will require deployment of new power plants. In support of NPP license renewal over the past decade, various national and international programs have been initiated. This paper reports part of the work performed in support of the U.S. Nuclear Regulatory Commissionpsilas (NRCpsilas) Proactive Management of Materials Degradation (PMMD) program. The paper concisely explains the basic principles of PMMD and its relationship to advanced diagnostics and prognostics and provides an assessment of some the technical gaps in PMMD and prognostics that need to be addressed.