In France, the ASN carries out a complete "check-up" on each NPP at intervals of 10 years, called the periodic safety review. This is an opportunity for in-depth inspection of the installations to check that they comply with all the safety standards. It is also an opportunity to compare the safety level of the installations with the more recent installations and to make the modifications considered to be necessary with a view to improving safety. In this respect, the safety reviews are one of the cornerstones of ASN policy, which is to ensure that not only does the licensee maintain the level of safety of its installations, but also improves it.

The safety reviews therefore have two primary objectives:

• firstly, to compare the level of safety of the facilities with their initial "safety reference framework" in order to identify any deterioration over time, as well as the faults and weaknesses of the safety analysis. This is the conformity review.
• secondly, to compare the safety of the facilities with the most recent safety standards, in order to improve the level of safety. This is the safety review. This review aims to identify modifications likely to bring about a significant improvement in the safety level and establish a new "safety reference framework". Advantage is taken of the 10-yearly reactor outages (see § 1.2.3) for deployment of these safety improvements.

The review process comprises an orientation phase, setting the topics and scope of the conformity and review studies, a study phase, the aim of which is to determine the modifications to be made, and a modifications review phase. After the study phase, the choice of topics for the reactor conformity review is finalised. Each of the phases in principle comprises a proposal from the licensee, consultation of the Advisory Committee for nuclear reactors and a position from the ASN. Before the first ten-yearly outage associated with the safety review, the review must rule on the acceptability of the new safety reference framework and the continued operation of the reactors following their ten-yearly outage.

The twenty-year safety review for the 900 MWe reactors

Implementation of the modifications arising from this safety review continued during the course of 2005 on the occasion of the second ten-yearly outages at Blayais 4, Cruas 1 and Saint-Laurent B1, and will end in 2010 with Chinon B4. Among the modifications made by EDF could be mentioned those aimed at improving the reliability of the backup turbine generator, the steam generators auxiliary feedwater system and the ventilation systems in premises housing safeguard equipment.

The thirty-year safety review for the 900 MWe reactors

After defining the guidelines for this periodic safety review in 2003, the ASN consulted the Advisory committee for nuclear reactors at the end of 2004 and in the first half of 2005 concerning the various study topics, in particular serious accidents, containment of radioactive materials, fire, explosion risks and the use of probabilistic safety studies. Subsequent to these consultations, the ASN requested modifications and additional studies for possible design or operation changes. Implementation of the modifications arising from this safety review is scheduled for the third ten-yearly outages on the 900 MWe reactors, from 2008 to 2020.

The twenty-year safety review for the 1300 MWe reactors

Review of the modifications resulting from this periodic safety review was completed in 2005 in accordance with the investigation process established by the ASN.

Implementation of the modifications resulting from this periodic safety review began in spring 2005 during the second ten-yearly outage of Paluel 2. It will continue on the other 1300 MWe reactors until 2014. Of the modifications implemented by EDF, particularly noteworthy are those designed to improve the fuel handling operations during refuelling outages, or activation of the backup pumps from the control room if the reactor's external electricity supply is lost.