For over a decade, the U.S. Department of Energy’s Light Water Reactor Sustainability (LWRS) Program has been advocating for the modernization of the existing fleet of commercial light water reactors (LWRs). These nuclear power plants (NPPs) play a foundational role for the U.S. in terms of both energy security and economic prosperity, and should therefore be maintained as essential assets in the national infrastructure portfolio. R&D projects under the Plant Modernization Pathway of the LWRS Program play a vital role in providing guidance on transforming existing LWRs into fully modernized NPPs. This report summarizes and highlights the role of Plant Modernization Pathway R&D in achieving the goal of safe and economical long-term operation of the nation's commercial NPPs.