Flood protection of nuclear facilities; La protection des installations nucleaires de base contre les inondations externes

As a consequence of the partial flooding of the Blayais nuclear power plant that took place in december 1999 during an exceptionally strong storm, the ASN (French authority for nuclear safety) asked all power plant operators to re-assess the safety of their installations in case of flood. New requirements concerning flood risks have been implemented which has allowed a better safety standard. In order to assure a better and more robust taking into account of the flood risk particularly at the very design stage of a facility, the ASN has published a set of rules. The phenomena at the origin of an external flood are reviewed. For each nuclear power plant flood risks have to be re-assessed and the functions and technical means that are necessary to maintain the reactor in a safe state in case of flood have to be identified and these functions and means have to be protected according to the principle of defence-in-depth. The feedback experience of the Fukushima accident confirms this approach. The application to the Blayais power plant and to the Cruas-Meysse power plant are briefly reported. (A.C.)