- 87 - 2 Earthquakes An earthquake is an event liable to lead to failures which could affect all the facilities on a site, in particular the systems important for safety. The possibility of an earthquake is factored into the design of the facilities and is periodically reassessed on the occasion of the periodic safety reviews (see § 1.3). The CSAs demonstrated that the current seismic margins on EDFs NPPs are sufficient to avoid cliff edge effects in case of limited exceeding of the current safety requirements. These CSAs confirmed the interest of the periodic reassessment of the seismic risk on the occasion of each ten-year periodic safety review. This process of seismic risk review at each periodic safety review should be continued. Furthermore, following the analysis of EDF's CSAs reports and the targeted inspections to which this led in the summer of 2011, ASN has identified several areas in which safety could be improved, related to the seismic robustness of the facilities. With regard to the seismic risk, ASN will therefore require that EDF: Ensures that the equipment used to control the basic safety functions is protected against fire in the event of an earthquake. The main measures to protect the facilities against fire are not at present all designed to withstand the facility's baseline safety requirements earthquake; Increases how this risk is taken into account in the day-to-day operation of its reactors: improved operator training, improvement in how the "event-earthquake" issue is considered, compliance with the fundamental safety rule concerning seismic instrumentation (maintenance, operator familiarity with the equipment, calibration). In a number of NPPs, ASN observed deficiencies in the application of the seismic risk safety requirements in force; For the Tricastin, Fessenheim and Bugey sites, provides a study analysing the seismic robustness of the dykes and other structures designed to protect the facilities against flooding and to present the consequences of a failure of these structures. Furthermore, following the Complementary Safety Assessments (CSAs) performed on the nuclear facilities in the wake of the Fukushima accident, ASN considers that the safety of the nuclear facilities needs to be made more robust to very unlikely risks that are not currently considered in the design of the facilities or following their periodic safety review, and to include this requirement in the regulatory framework. These facilities must be given the resources enabling them to deal with, such as: combination of natural phenomena of an exceptional scale, greater than the phenomena considered in the design or the periodic safety review of the facilities very long-term loss of electrical power supply or cooling function situations which could affect all the facilities on a particular site. ASN will thus be requiring that the licensees set up a "hard core" of material and organisational measures to guarantee the operational nature of the structures and equipment, such as to be able to manage the basic safety functions in these exceptional situations. This subject is developed further in part 16 of this report. 2.1 Design of the facilities In addition to the facility's initial seismic design, and during the course of the reactor second and third ten-yearly outage inspections (VD2 and VD3), ASN specifically requested that the changes to the safety requirements and new scientific knowledge in the field of this hazard and the paraseismic justification to be taken into account. It is important to note that the updating of the Safe Shutdown Earthquake SSE on the site is simply one aspect of the periodic safety reviews regarding the seismic field. The development of methods and computing resources used for paraseismic engineering has fine-tuned the evaluation of the seismic strength of buildings and equipment. Reinforcements may therefore be decided, not simply on the basis of a reassessment of the hazard,
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