The Advanced Light Water Reactor (ALWR) Utilities Requirement Document (URD) was established through the efforts of the U.S. Electric Power Research Institute (EPRI) and the participation of both U.S. and international utilities. The URD uses the large experience base from existing light water reactors to minimize the risk to the plant owner, provide confidence relative to credibility of costs and schedules, and eliminate the need for a plant prototype. The URD consistently emphasizes the use of proven technology to achieve these objectives. The AP600 program has strictly followed the requirements and guidance specified in the URD, and has incorporated proven technology into all aspects of the design. The entire URD process contributes directly to the use of field-proven technology because the URD captures the lessons learned from over 20 years of operating plant experience, identifies the best practices, and incorporates these as design requirements. Over 5000 design requirements are identified in the URD.