[en] The Nuclear Regulatory Commission's (NRC) guidance, NUREG-1407, on performing Individual Plant Examinations for External Events (IPEEE) allows a Seismic Margins Assessment (SMA) to address the IPEEE seismic issue regarding the survivability of plant equipment during a seismic event and the capability of the plant to safely shutdown following the seismic event. The NRC guidance further allows the use of the NRC SMA approach or the Electric Power Research (EPRI) approach to evaluate these issues. In addition, the NRC's Unresolved Safety Issue A-46 (USI A-46) can also be efficiently addressed with the EPRI SMA evaluation. These methodologies are useful in determining a minimum list of equipment required for safe shutdown (i.e., Safe Shutdown Equipment Lists). The resultant Safe Shutdown Equipment List, SSEL, is used to identify the electrically powered equipment required for safe shutdown for which a relay evaluation is required. The evaluation of relays associated with safe shutdown equipment is necessary since equipment can fail to operate properly due to mechanical failure or improper operation/actuation due to relay failure. SAIC has performed relay evaluations on five nuclear power plants. This paper is intended to summarize the practical insights and lessons learned from use of the EPRI SMA approach

No abstract available

[en] The existing instrument air system at Turkey Point station uses mobile diesel-driven air compressors. Although these diesel compressors have performed their function well, they represent a maintenance and financial burden requiring engineering review. An engineering evaluation is ongoing to develop several feasible conceptual design options to upgrade the instrument air systems. This phase-1 study was performed to assess the reliability of the various proposed design options. A phase-2 study will be conducted later to determine the core damage frequency for a selected option

[en] The events at Fukushima Daiichi taught us that meeting a deterministic design basis requirement for external hazards does not assure that the risk is low. As observed at the plant, the two primary reasons for this are failure cliffs above the design basis event and that combined hazard effects are not considered in design. Because the possible combinations of design basis exceedences and external hazard combinations are very large and complex, an approach focusing only on the most important ones is needed. For this reason, a risk informed approach is the most effective approach, which is discussed in this paper. (author)