DEFENSE-IN-DEPTH APPROACH FOR USE IN A RISK-INFORMED, TECHNOLOGY-NEUTRAL DESIGN AND LICENSING FRAMEWORK FOR NEW NUCLEAR PLANTS

The regulatory framework for the current generation of operating plants and advanced light water reactors (ALWRs) planned for near term construction has evolved over several decades to permit effective regulation of the light water reactor designs. To address other reactor types, development of a framework that possesses the attributes of being technology neutral, risk-informed and performance-based with corresponding processes (regulations and guidance) is ongoing by several U.S. and international organizations. A key design and operating principle which is applied to existing plants and will continue to be applied to future plants is defense-in-depth. The advent of advanced reactor designs, some of which are not based on light water reactor technology, provides incentive for changes in the regulatory framework in several areas, including defense-in-depth practices. To support development of an integrated framework, the Electric Power Research Institute (EPRI) conducted research to identify and assess specific elements of possible technology neutral, risk-informed, performance based frameworks that had been proposed by others. The intent was to develop a preliminary framework based on the results of this review and evaluation and to provide recommendations in areas where additional development and testing would appear to be most beneficial. "Technical Elements of a Risk-Informed, Technology-Neutral Design and Licensing Framework for New Nuclear Plants", EPRI Report 1016150 documents this research (Reference [1]). For defense-in-depth (D-in-D) existing viewpoints from various sources were compared and an alternative integrated approach which addresses key issues was developed. These alternative views are contained in publications such as NUREG-1860 [2], Regulatory Guide 1.174 [6], IAEA Safety Standards Series No. NS-R-1 [3], IAEA 75-INSAG-3 Revision 1 [4], INSAG-12 [4], and IAEA INSAG-10 [5]. The results of this research support the ongoing efforts to develop standards and guidance for advanced plants with safety characteristics which differ from existing and advanced LWRs.