Equipment or component obsolescence

The availability of spares which have been qualified for installation in the reactors is highly dependent on any changes occurring within the suppliers' industrial situation.

Should the manufacturer cease to make certain components, or simply go out of business, this could create spare procurement problems for certain systems.

New spares would then require safety justification before they could be installed in the reactors.

Given the length of this procedure, the licensees must adopt a vigorous forward-looking policy in this area.

The ability of the facility to follow changes in safety requirements

Greater knowledge and technological improvements, as well as changes in the social acceptability of risk are also factors which can lead to the decision that an industrial facility requires extensive renovation work or - if this cannot be done at an acceptable cost - to closure at a time in the future to be defined.

This "defence in depth" type strategy is based on three lines of defence.

Including ageing in the design

The design and manufacture of components, the choice of materials and the installation arrangements must be tailored to the intended operating conditions and take account of the known or presumed deterioration processes.

Monitoring and anticipating ageing phenomena

Deterioration phenomena other than those included in the design may be brought to light during the course of operation. Monitoring and preventive maintenance programmes and conformity reviews (see § 2.2.1), or review of experience feedback are ways of detecting these phenomena.

Repairing, modifying or replacing equipment likely to be affected

This type of action has to be planned in advance, given the procurement lead-times for new components, the maintenance preparation time, the risk of obsolescence of certain components and the risk of gradual loss of staff technical skills.

From a strictly regulatory standpoint, in France there is no limit on the time that a nuclear power plant is authorised to operate.

However, the ministers with responsibility for nuclear safety may at any time ask a licensee to conduct a safety review of its facility. The practice in France is thus to conduct a safety review every 10 years. These reviews are a particularly good opportunity for an in-depth examination of the effects of ageing, but also of the need for and feasibility of modifications to be made if the facility is to keep pace with changes in the safety requirements (see § 2.3.2).

In preparation for the 900 MWe reactors third ten-yearly outages, the ASN therefore in 2001 asked EDF to present a precise account of the ageing status of each reactor concerned and demonstrate the possibility of continuing with operation beyond 30 years in satisfactory safety conditions.

In reply to this request, Electricité de France drew up a programme of work which was examined by the Advisory Committee for nuclear reactors in December 2003. The organisation set up by EDF under the terms of this programme, and the methodology used to take account of ageing were considered on this occasion to be satisfactory. In 2005, EDF sent the ASN the initial data resulting from implementation of this programme. These data will be reviewed on a number of occasions by the Advisory Committee for nuclear reactors and the Standing Nuclear Section (SPN) of the Central Committee for Pressure Vessels. At the end of this examination process, the ASN will adopt a stance for each individual reactor regarding continued operation beyond the third ten-yearly outages