ASN's guide to help licensees or applicants take better account of the flood risk in nuclear facilities

ASN Guide N^o13 relative to "the protection of basic nuclear installations against external flooding" is intended for the licensees or applicants and contains recommendations for assessing and quantifying the external flood hazard faced by these facilities and for determining the appropriate means of protection adapted to the specifics of the flooding hazard.

The preparation of this guide follows on from the lessons learned after the partial flooding of the Blayais nuclear power plant in the storm of December 1999. This event had led the licensees, under the oversight of ASN, to reassess the safety of their facilities with respect to the flood hazard under more severe conditions than before, and to make many improvements to enhance the protection of their facilities against the flood hazard.

In parallel with these first concrete measures to improve existing facilities ASN set up - as of 2005 - a working group to conduct an in-depth analysis and develop provisions applicable to any new basic nuclear installation based on the advances in knowledge so that the external flood hazard could be taken into account more fully and more robustly from the facility design stage.

This ASN Guide N^o13 applicable to new and existing basic nuclear installations is the result of a process of consultation and discussion with the stakeholders spanning eight years and comprising four major phases:

• the setting up of a working group coordinated jointly by ASN and IRSN (French Institute for Radiation Protection and Nuclear Safety) and bringing together organisations specialised in hydrology, hydraulics and meteorology, along with representatives of the licensees. Set up in 2005, the working group completed its work and submitted a first draft guide in December 2009;
• a public consultation on the draft guide held from 15^th June to 15^th September 2010, which resulted in the submittal of more than 350 modification proposals;
• technical discussions between IRSN and the licensees from February to October 2011 to identify the guide amendment proposals that were agreed upon;
• obtaining the opinion of the advisory committees of experts on nuclear reactors (GPU) and laboratories and plants (GPU), issued on 24^th May 2012, on the points for which reservations still existed.

The final version of ASN Guide N^o.13 approved by the ASN Commission on 8^th January 2013 supersedes the former basic safety rule "RFS 1.2.e" dated 12^th April 1984.