- 144 - effects characterised by a shorter time before core exposure than that specified for deployment of the FARN means. Regarding the external measures planned to prevent the fuel being damaged, EDF has specified in its CSA reports for the reactors in service that the measures are identical to the preceding case of loss of the off-site electrical power supplies and the conventional backup supplies. For the EPR, EDF has specified that the design measures (redundant, diversified and robust electrical power sources) and the associated external measures help prevent damage to the fuel. The external measures for managing situations of loss of the off-site electrical power supplies and the conventional backup supplies, and any other on-site emergency source examined by EDF in its complementary safety assessments correspond to the requirements of ASN decision 2011-DC-0213. Regarding the measures that can be envisaged to prevent cliff-edge effects or to increase the robustness of the facility, apart from the measures proposed in the event of loss of the off-site electrical power supplies and the conventional backup supplies and described earlier, EDF has proposed in the CSA reports: for the 900 MWe series, to study resetting of the EFWS system turbine-driven pumps from the control room (for the states in which this is possible); for the 1300 MWe and N4 series, and for states where the primary system is just open, to change the primary system pressure build-up procedure to remove the residual power by the steam generators, thereby having sufficient secondary pressure to supply the required turbine-driven auxiliary feedwater pump and maintain the required water inventory of the SG when the primary system can be pressurised again; for the EPR: o to extend the electrical supply for the functions supplied by the "12-hour" batteries by implementing supplementary fixed or mobile electrical power sources; o to put in place a means of restarting the severe accidents I&C in the event of it is has been cut-off; o to put in place devices and mobile electrical power supply means necessary to: ensure the habitability of the control room, for the spent fuel pool, supply one cooling channel of the PTR system or a water make-up from the tank of the JAC system; o to integrate the essential information concerning the development of the situation in the fuel building (fuel pool temperature, water level measurement, etc.) on the severe accidents I&C and the severe accidents console (PAG) which are supplied by the "12-hour" batteries. ASN has observed that EDF proposes measures to increase the times before the core becomes exposed, including: deploying additional pumping means to make-up the primary and secondary systems; operating procedure studies and changes to limit the risk of a breach at the RCP seals if their cooling is lost; increasing the autonomy of the feedwater supply for the steam generators and the primary cooling system. ASN considers that it is necessary for EDF to effectively increase the time lapses before the core becomes exposed. It considers that the supplementary measures proposed by EDF, which will increase robustness in the event of loss of the electrical power supply and the cooling water, must be implemented. 5.1.4 Conclusion on the planned measures to protect the facilities against the risk of electrical power supply loss In its conclusions to the CSA reports, EDF considers that the backup means provided to cope with total and summed loss of the electrical power sources ensure good robustness of the facilities, particularly given the number of lines of defence included in the design and assumed to be lost in a deterministic manner in the required scenarios.
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