- 145 - ASN observes in the CSA reports that EDF has performed the assessment relative to electrical power supply losses without considering that they could be caused by an external hazard (earthquake, flooding, etc). Yet such an external hazard can lead to failure of the equipment planned to be used to counter the loss of the electrical power supplies. ASN therefore considers that the times before the fuel suffers damage in the event of electrical power supply loss could be shorter than those indicated by EDF in the CSA reports, particularly if the power loss was induced by an earthquake or a flood. ASN considers that EDF must improve the hazard robustness of some of the proposed supplementary measures for managing electrical power loss situations. ASN will instruct EDF to propose during 2012 a "hard core" of material and organisational measures that will be subject to more stringent requirements, particularly with respect to the earthquake and flooding risks (see § 8). 5.1.5 Measures envisaged to enhance facility robustness with respect to electrical power supply losses EDF has summarily proposed in the CSA reports the following measures to counter the risk of a loss of the electrical power supplies for the reactors in service a hazard-resistant generator set called the "ultimate backup diesel generator" will be installed on each reactor; it will be able to deliver electrical power for : o the minimum necessary I&C and control room lighting, o the information required in case of loss of spent fuel pool cooling, o the ultimate water make-up pump for replenishing the EFWS system tank, the PTR system tank and the spent fuel pool, o the information necessary in core meltdown situations, o the containment isolation valves, the ventilation filtration of the control room and the ventilation filtration of the inter-containment space, o one motor-driven pump of the EFWS system and a make-up for the primary system; in an initial phase pending installation of the "ultimate backup diesel generator", two small fixed generator sets will be provided: o one to supply the minimum reactor I&C and control room lighting, o the other to supply the ultimate water top-up pump for replenishing the EFWS system tank, the PTR system tank and the spent fuel pool; the possibility of resupplying power in the short term to the functions necessary for managing losses of spent fuel pit cooling shall be studied; enhancing the operating reliability of the LLS in the event of a temperature rise in the buildings beyond 24 hours without ventilation will be studied, and modifications will be proposed if revealed necessary by the studies. For the EPR reactor, EDF has proposed the following measures in the CSA reports: extending the autonomy: mobile means of pumping fuel from the main generator set tanks to replenish the SBO generator sets; extension of the duration of electrical supply for essential functions by deploying supplementary fixed or mobile electrical power sources; means of restarting the severe accidents I&C. During the examination of the CSA reports by the IRSN, ASN's technical support organisation, EDF took the following commitments: in order to ensure simultaneous injection at the seals on the 900 MWe series reactors, where there is only one RCV system charging pump for two reactors, EDF will carry out a study to determine the appropriateness of the flow that supplies the primary pump seals of each of the two reactors, in the event of loss of the off-site electrical power supplies and the site backup energy sources; the results of this study should be available at the end of the first quarter of 2012;
RkJQdWJsaXNoZXIy NjQ0NzU=