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Following the accident at the Fukushima Daiichi nuclear power plant resulting from the March 11, 2011, Great Tohoku Earthquake and subsequent tsunami, the NRC established the Near Term Task Force (NTTF) in response to Commission direction. The NTTF issued a report that made a series of recommendations, some of which were to be acted upon "without unnecessary delay." Subsequently, the NRC issued a 50.54(f) Letter that requests information to assure that these recommendations are addressed by all U.S. nuclear power plants. This report provides guidance for conducting seismic walkdowns as required in the 50.54(f) Letter, Enclosure 3, Recommendation 2.3: Seismic . Every U.S. nuclear power plant is required to perform seismic walkdowns to identify and address degraded, non-conforming or unanalyzed conditions and to verify the current plant configuration with the current seismic licensing basis. The nuclear power industry and the NRC agreed to cooperate in the development of guidelines and procedures to perform these walkdowns.
ObjectiveThe objective of the work reported in this document is to provide guidance on the performance of plant seismic walkdowns to satisfy the requirements of NTTF Recommendation 2.3: Seismic.
ApproachThe approach taken was to formulate guidance for the seismic walkdowns by using a sampling procedure that aligns the scope of the effort with the required schedule while achieving the objectives of the walkdowns as described in the NRC 50.54(f) Letter. The sample includes representative items of equipment needed to safely shut down the reactor and maintain containment integrity. In some cases, equipment lists from the Individual Plant Examination for External Events (IPEEE) that were developed for plants in the early 1990's can be used to identify the sample items. The sample needs to be suitably diverse across a spectrum of plant safety-related equipment including different classes of equipment. In keeping with the lessons learned by over thirty years of industry investigation of earthquake effects on mechanical and electrical equipment, the Seismic Walkdown Guidance includes a focus on equipment anchorage and seismic spatial interactions, as well as consideration of other potentially adverse seismic conditions such as seismically-induced fire and seismically-induced flood.
ResultsThis report provides guidance and procedures to perform the Recommendation 2.3: Seismic walkdowns including selection of personnel, selection of a sample of SSCs that represent diversity of component types and assures inclusion of components from critical systems/functions discussed in the NRC letter, conduct of the walkdowns, evaluation against the plant seismic licensing basis, and reporting requirements. The report includes checklists to be used by the Seismic Walkdown Engineers for seismic evaluations.
Application, Value and UseThe guidance in this report is intended for use by all U.S. nuclear power plants to meet the requirements of NTTF Recommendation 2.3: Seismic. The primary value in this guidance is that it has been reviewed with the NRC and can be applied by all plants to provide a uniform and acceptable industry response to the NRC. The guidance will also be used as the basis for development of an industry training course to further assure its proper application.
EPRI PerspectiveThe schedule for satisfying the requirements of Recommendation 2.3: Seismic is aggressive. The guidance therefore must be generic and endorsed by the NRC so that it can be applied uniformly across the U.S. industry. This report was produced with extensive input and participation from utility seismic engineers and similarly extensive review by the NRC.
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