- 105 - This method complements the studies and includes a field cross-check of the actual condition of the equipment, systems and structures necessary for reactor safe shutdown (design, qualification, anchors, foundations, etc.). This type of inspection also allows identification of the points which, if improved, would reinforce the robustness (construction measures, protection, relocation of equipment and so on). It is a different but complementary review of the approach for checking the design-basis earthquake conformity of the equipment. With regard to the Tricastin site, the study showed the robustness of the facility and the conservative nature of the engineering practices used in the construction, which are consistent across all the power plants in service. Over and above the search for a higher hazard margin, one benefit of this type of study lies in the cross-checking of the real condition of the equipment and the implementation of good practices in addition to the conformity baseline. Another advantage is that, on the basis of hypotheses, methods and criteria that are different but which are consistent with those adopted at the design, this type of method makes it possible to check that all or part of the safety objective has been met. When processing a nonconformity on the PTR12 tanks at Bugey, EDF carried out a CP0 robustness study which was in some ways similar to the SMA approach. Following these studies, anomalies were detected in the design of the anchors, leading to appropriate corrective actions. This confirms the potential benefits of these methods. ASN considers that using SMA type assessments for verification of the French nuclear power plant reactors, is of very real interest and considers that the development of review methods for equipment, systems and structures, in order to implement the best practices resulting from these assessments or from operating experience feedback should be generalised. ASN will be asking EDF to include this topic in the forthcoming periodic reactor safety reviews. In addition to the SMA approach, on the occasion of the 1300 MW periodic safety review, EDF proposed an experimental seismic probabilistic safety assessment (EPS) for the Saint Alban site. This subject is today being investigated and cannot therefore be implemented in the complementary safety assessments. EDF seismic inspections on equipment necessary for reactor operation in the event of total loss of off-site and on-site power supplies beyond the design-basis earthquake. EDF carried out a study of the seismic behaviour (guaranteed functionality, satisfactory anchors, absence of interactions with nearby equipment and structures) of the main equipment items not seismic-classified and necessary in this situation. EDF identified a deficiency on the SER13 and PTR tanks, the CRF14 valves on certain sites, some electrical cabinets and a number of interactions to be considered. In its reports, EDF stated that it will be initiating studies into reinforcing the robustness of these items. Furthermore, some equipment requires special studies and, as applicable, modifications (valves on certain SAR15 tanks, etc.). As a result of these inspections, EDF identified the following areas for vigilance and complementary improvement measures for a hazard beyond the design-basis earthquake: Electrical equipment: Some equipment is not seismic-qualified or, if so qualified, its functional behaviour beyond the DBE is not guaranteed. EDF will thus be identifying the equipment required to manage loss of heat sink, loss of electrical power, severe accident situations and topping up the spent fuel pools. It will be proposing a programme of action to render them robust. 12 PTR: reactor cavity and spent fuel pool cooling and treatment system. The PTR acts as a tank for the safety injection system (RIS) 13 SER: Conventional island demineralised water distribution system 14 CRF: Circulating water system 15 SAR: Instrument compressed air distribution system.
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