Further to flooding of the Blayais site in December 1999, EDF undertook steps aimed at reassessment and protection of the sites against external flooding hazards. This reassessment particularly concerns the revision of the maximum design flood level, or CMS (maximum water level used in the design of the plant protection structures), the additional events which could lead to flooding of the sites, such as particularly heavy rainfall, a break in the water storage tanks, a rise in the water table, as well as the course of action to be followed in the reactors if the water level were to rise. A file was produced for each site and protection improvement works have been defined.

The work made necessary by the flood risk reassessment is in progress and EDF has undertaken to complete work concerning the risk of water ingress by the end of 2007. In particular, the building permit for a peripheral protection dyke around the Belleville plant was issued and construction should begin in the first quarter of 2006. Construction of a peripheral wall around the Bugey site is also in progress and should be completed at the end of 2006.

The ASN considers that the progress of studies and work is as expected. Nonetheless, for the particular case of the Tricastin NPP, the CMS review studies are not yet complete. Additional studies to check the strength of the infrastructures located on the Rhone river upstream of the plant are nearing completion. The results of these studies are expected for early 2006.

At the end of 2004, the ASN asked the Advisory Committee for nuclear reactors and the Advisory Committee for laboratories and plants for their recommendation in order to rule on the overall approach to the external flooding risk affecting EDF reactors. The situation of the other nuclear installations will be reviewed on this same occasion, which justifies a joint meeting of the two Advisory Committees.

At the same time, a first meeting of the working group for revision of RFS I.2.e to deal with the flooding risk, was held in 2005. This group consists of experts, licensee representatives and the ASN. The new BNI flooding risk protection guide will cover the choice of unexpected events likely to lead to flooding of the site, and the methods used to characterise such events. It will apply to all BNIs.

Fire risk

The fire risk in EDF's nuclear power plants is dealt with using the principle of defence in depth, based on:

– prevention, primarily consisting in:

• ensuring that the type and quantity of combustible materials present in the premises remains within the sectoring design limits (fire doors and walls, etc.);
• identifying and analysing the fire risks. In particular, a fire permit must be issued and protective measures taken for all work likely to start a fire;

• the principle of splitting the installation up into sectors designed to contain the fire within a given perimeter;
• protection of redundant equipment which performs a safety function;
• firefighting, which should enable a fire to be tackled and extinguished within a time compatible with the duration of the fire and the fire-resistant capability of the fire sectors.

Prevention

With regard to prevention, EDF has implemented its new system of "fire permits" in the plants.

The ASN has noticed improvements since 2004 in the drafting of the fire permits and their actual use in the plants. It does however feel that the steps taken must be actively pursued, in particular with respect to risk analysis and identification and implementation of protective measures.

In 2005, the ASN checked the progress of the work being done to identify the areas storing fire loads during reactor outages and will analyse all the corresponding studies with the assistance of its technical support organisation. Inspections will be scheduled by the ASN in order to check the conditions in which these premises are used.

Design

With regard to design, EDF is continuing to deploy the fire action plan (PAI), to ensure the conformity of and improve fire protection for the 900MWe and 1300 MWe reactors. During the course of the 2005 inspections and six-monthly meetings with EDF, the ASN considered that the PAI was being satisfactorily assimilated and that EDF was on-track to meet the completion dates set for the end of 2006 by the decision of 12 September 2000.

As part of the thirty-year safety review of the 900 MWe reactors, the ASN in March 2005 consulted the Advisory Committee for nuclear reactors about the modifications to be made to these reactors in addition to the current design:

• through the use of the results of fire probabilistic safety studies (EPS), to supplement the deterministic studies,
• through evaluation of the existing design margins of the fire-resistant items, in the light of the fire durations estimated for the premises.

The ASN considers that the results of the probabilistic studies are satisfactory and that the fire EPS approach should be continued by EDF for the 900 MWe reactors.

Furthermore, with regard to evaluation of the existing margins, the ASN considers that the modifications presented by EDF would be such as to improve the safety of the 900 MWe reactors. EDF will complete its evaluation by ensuring that the inventory of premises checked is exhaustive and that there is no snowball effect in relation to the margins chosen.

The order of 31 December 1999 which lays down the general technical regulations designed to prevent and mitigate detrimental effects and external risks resulting from the operation of BNIs, also defines stipulations regarding fire protection. In 2005, the ASN drafted an application guide for the above-mentioned order dealing with the fire risk and prepared a draft order modifying and improving the previous one.