- 204 - Earthquake The complementary safety assessments demonstrated that the current seismic margins on the EDF nuclear reactors are satisfactory, in particular thanks to the periodic revision of the seismic risk on the occasion of each ten-yearly periodic safety review. These margins are the result both of the conservative values adopted for the seismic level considered and the application of paraseismic standards used for the design, the periodic safety reviews and the qualification of SSC. Flooding With regard to flooding, the complementary safety assessments show that the complete reassessment carried out following the flooding of the Le Blayais nuclear power plant in 1999 offers the installations a high level of protection against the risk of flooding. Management of severe accidents Improvements have been made to the reactors in operation and are designed into the EPR reactor, owing to the work achieved since the Three Mile Island accident. ASN is also making efforts to ensure that limiting radioactive releases into the environment in the event of any accident (with or without core melt) is a major objective of the continuous process to improve the safety of the installations. This process in France is in particular organised around the ten-yearly periodic safety reviews, which aim to enhance the baseline safety requirements applicable to the installations. EPR reactor For the Flamanville 3 EPR reactor, ASN considers that the safety objectives and the strengthened design of this type of reactor already offer improved protection against severe accidents. Its design in particular takes account of and incorporates measures to deal with the possibility of accidents with a core melt and combinations of hazards. Furthermore, all the systems necessary for the management of accident situations, even severe, are designed to remain operational for an earthquake or a flood as defined in the baseline safety requirements. 8.2 Identified safety problems Loss of electrical power supplies and loss of cooling systems EDF analysed loss of heat sink and loss of electrical power supply situations for the reactors, which go beyond the situations studied in the current baseline safety requirements, in particular considering that the postulated situations are assumed, on the one hand, to affect all the reactors on a site, on a long-term basis and, on the other, to be possibly the result of an off-site earthquake or flooding, including of a level higher than that considered in the current baseline safety requirements. Analysis of EDF's CSA reports showed that certain heat sink and electrical power supply loss scenarios can, if nothing is done, lead to core melt in just a few hours in the most unfavourable circumstances. 8.3 Strengthening of nuclear safety and forthcoming work Conformity of installations The deviations identified by the CSAs do not directly compromise the safety of the facilities concerned but, especially if they combine, they can constitute factors such as to weaken them. ASN will thus be requiring that the licensees tighten up the detection and processing of nonconformities. ASN will in particular be proposing that the regulations on this topic be strengthened via the draft order setting out general rules for basic nuclear installations, in particular with regard to assessing the cumulative impact of any deviations present in a facility. These stipulations will be backed up by ASN requirements.
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