- 173 - As indicated earlier, ASN considers that failure of the means of communication in an emergency situation is unacceptable, therefore it is vital to reinforce them. ASN will therefore require EDF to integrate in the "hard core" of reinforced material and organisational provisions, the communication means that are vital for emergency management. In the CSA reports, EDF presents the conclusions of its analysis concerning the H1 and H3 situations. These analyses however do not consider that an external hazard can be the cause of such situations. Consequently, the times given in these reports for the H1 and H3 situations alone are not representative of cases where these situations are induced by an earthquake or flooding, even with the hazard levels of the current baseline safety standard. This is because the current baseline includes no systematic requirement regarding the earthquake resistance and flooding protection of the equipment used in H1 and H3 systems. ASN observes certain weaknesses regarding the ability of the facilities to withstand a whole-site H1 or H3 situation induced by an earthquake, including the earthquake level of the current baseline safety standard or flooding beyond the baseline safety standard. ASN takes note of the measures envisaged by EDF to improve the robustness of the facilities with respect to these situations and which consist in making the complementary provisions defined for the whole-site H3 situation robust to earthquakes, and studying means for guaranteeing protection of the H1/H3 equipment against a flood exceeding the baseline safety standard. ASN will ask EDF for additional proof of the improvement of facility robustness against these situations. Loss of electrical power supply: Total loss of electrical power supplies (loss of the off-site sources and the on-site diesel generators) is a situation taken into account in the severe accident management guide (GIAG). This situation could moreover lead to loss of the telecommunication means used in normal operation. The dynamic containment achieved by the ventilation systems would be lost, and particularly the main control room ventilation function and the filtration of that ventilation via the iodine trap. Permanent habitability of the control room is guaranteed, unless the U5 system filter is opened, in view of the modifications presented in the CSA report. If the U5 system is used, the habitability can be temporarily compromised. In this respect, EDF has planned to reinforce the electrical backup of control room ventilation and filtration through the Ultimate Backup Diesel Generator (DUS). Pending implementation of this modification, the FARN will deploy means to ensure the electrical backup of these equipment items for the damaged reactor. As indicated earlier, ASN considers that control room habitability must be ensured if events presenting risks for operator safety should arise, such as the release of hazardous substances into the environment or opening of the U5 system filter. ASN will issue a requirement on this subject. As indicated earlier, ASN considers that loss of the telecommunication means in the event of electrical power supply loss is unacceptable. The telecommunication means must therefore be reinforced in this respect. ASN will require EDF to integrate the telecommunication means necessary for emergency management into the "hard core" of reinforced material and organisational provisions. Potential failure of the instrumentation: The instrumentation helps optimise management so as to delay or prevent entry into a severe accident situation if possible. In its CSA reports, EDF indicates that the situation diagnosis and prognosis are established by the emergency teams on the basis of the measurement of certain identified parameters. In case of loss of the electrical power supplies, the instrumentation that detects entry into the SA situation is no longer available in the control room. EDF has undertaken to ensure the electrical backup of this instrumentation by adding an Ultimate Backup Diesel Generator (DUS). However, in the event of an earthquake, the availability of the instrumentation useful in SA situations is not guaranteed because it is not earthquake classified. In addition, as the containment pressure sensor is not backed up by the backup turbine generator (LLS), it will be unavailable in the event of electrical power supply loss. EDF plans for the electrical backup of this sensor by the FARN in order to counter the overall loss of the electrical power supplies.
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