Deregulation of the electricity market leads EDF to control its expenditure. Optimising maintenance costs is one way for EDF to improve its competitiveness. EDF has therefore developed a "maintenance reduction" project which aims to concentrate maintenance on equipment which would constitute a safety, radiation protection or operational risk in the event of failure, and is relying on maintenance methods which do not require equipment disassembling.

A first change occurred in the mid-90s with implementation of the "reliability centred maintenance" (RCM) method. This is the result of a functional analysis which determines the type of maintenance to be carried out according to the consequences of equipment failure on the system concerned, rather than simply according to their causes, as in the previous approach. The ASN considered that this approach did not compromise safety. Further to requests from the ASN and to take account of experience feedback from the plants, EDF revised the RCM method to deal with redundancy loss and common mode failures, as well as failure modes that could not be detected from the control room.

Taking advantage of standardisation of the NPPs in France, EDF is developing the concept of "pilot equipment" based maintenance, creating technically homogeneous families of similar equipment operated in the same way. The selection and close monitoring of a limited number of these items - which then act as pilot items within these families - could, if no deterioration is detected, spare systematic monitoring of all the items.

The ASN is closely monitoring how EDF takes account of experience feedback about the behaviour of the equipment concerned by these maintenance methodology changes, in particular with regard to the content and frequency of the inspections.

The scientific applications contributing to the safety demonstrations are subject to the requirements of the order of 10 August 1984 concerning the quality of the design, construction and operation of BNIs (see chapter 3, point 2.2.1). One of the key requirements is qualification, which consists in ensuring that the application can be used in complete confidence within a specific field.

On the occasion of the inspections into this subject, the ASN observed significant shortcomings concerning the inventory of scientific applications used in the safety demonstrations, the production of qualification files and the supervision of these files, particularly in the case of subcontracted studies

In 2005, the ASN asked EDF to take the necessary corrective action. In response, EDF proposed an organisation common to the various entities for implementation of the scientific applications used in the studies supporting the safety demonstration. The ASN will examine implementation of this organisation scheduled for 2006, in particular through inspections.