- 100 - There is only one emergency generator per site, which is not designed to withstand an earthquake. In the event of a common mode affecting all site backup diesels, only one of the site units could be backed up. In the event of an earthquake, the availability of this emergency generator cannot be guaranteed. ASN sees this as a weak point in the ability of the facilities to deal with an on-site H3 situation, in particular if resulting from an earthquake. ASN duly notes the measures envisaged by EDF to improve the robustness of its facilities vis-à-vis these situations, which in particular consist in ensuring the earthquake robustness of the additional measures defined for the on-site H3 situation. These aspects are also described further in § 5. ASN considers that the reinforcement objectives proposed by EDF are satisfactory. ASN will thus require that EDF increase the life of its batteries and supplement the electrical backup by emergency diesels, allocated to each reactor, which will have to be a part of the hard-core (see § 8) and will therefore have to withstand significantly higher seismic levels than the DBE. Conditions for access to the site following an earthquake: In the event of major disruption to roads and structures, the emergency response organisation calls on the public authorities who, in addition to triggering the off-site emergency plan (PPI) if necessary, take special measures. These measures allow on-call personnel to be brought in. The plant safeguard systems requiring external supplies (fuel, oil, etc.) have an autonomy of several days, varying according to the systems and described in the safety analysis report. ASN observes that EDF has not demonstrated site autonomy for a period of fifteen days (time considered by EDF for restoration of the off-site power supply) in all circumstances, in particular following an earthquake or flooding leading to the site being isolated (these aspects are detailed in § 5 of this chapter). ASN will require that EDF secure its on-site stocks of fuel and oil and ensure that they can be replenished in all circumstances, to guarantee an autonomy of at least 15 days. Earthquake-induced fire risk: The buildings consist of sectors to prevent the propagation of a fire. These sectors comprise a seismic strength requirement. The buildings and premises housing IPS equipment are subject to general equipment installation requirements to prevent the loss of the safety function in the event of a fire (in particular, redundant systems must not be installed in the same sectors, cables must be geographically separated whenever possible, and so on). Fire-fighting systems are subject to seismic strength requirements and they are separated from non-seismicclassified parts by seismic-classified isolating devices. However: the sectoring, fire detection and fixed extinguishing systems are designed to withstand to half of the DBE for the 900 MW and 1,300 MW plant series; operating experience feedback mentions outbreaks of fire in normal operating situations on IPS equipment; fire detection and fixed extinguishing systems are not electrically backed-up by seismic qualified equipment; seismic qualification of fire detection only applies to equipment installed within the context of the study of the reference accidents in the safety analysis report. ASN will require EDF to reinforce the fire sectoring, fire detection and fixed extinguishing systems so that they can withstand a SSE, and electrically back up the detection and control systems of fire protection system with seismic-qualified equipment.
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