LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT 2.5 Conformity and maintenance of the installations 2.5.1 – Maintenance of the installations and management of subcontracted activities Maintenance of the installations Preventive maintenance is an essential line of defence in ensuring the conformity of a facility with its baseline safety requirements. In order to improve the reliability of the safety-important equipment but also the industrial performance, EDF is optimising its maintenance activities, drawing on practices used in conventional industry and by the licensees of NPPs in other countries. In 2008, EDF decided to deploy the maintenance methodology known as “AP913”, developed by American nuclear licensees and based on two main principles: organisational changes to enhance monitoring of the reliability of the equipment and systems and implementation of a new type of preventive maintenance programmes. The AP913 implementation diagnostic performed by EDF in mid2016 revealed difficulties with implementing performance monitoring and with the increase in the maintenance tasks generated by the AP913 maintenance programmes. In 2017, EDF thus defined strategic guidelines for maintenance and reliability. It specified the roles of the various departments and professions related to the performance of maintenance, by reaffirming that the maintenance departments are responsible for the project ownership of the equipment they maintain, in particular in a context of continued operation of the reactors beyond 40 years. EDF also adopted function reviews to obtain an integrated view of the equipment and systems participating in each function, as well as implementing a new phase of its project to control the volume of maintenance. The aim of this approach is to propose tools and methods for adjusting preventive maintenance volumes. Management of subcontracted activities Reactor maintenance operations are to a large extent subcontracted by EDF to outside contractors. EDF justifies the use of subcontracting by the need to call on specific or rare expertise, as well as the highly seasonal nature of reactor outages and thus the need to absorb workload peaks. EDF’s decision to resort to subcontracting must not compromise the technical skills it must retain in-house in order to exercise its responsibility as licensee with regard to the protection of people and the environment and to be able to effectively monitor the quality of the work performed by the subcontractors. Poorly managed subcontracting is liable to lead to poor quality work and have a negative impact on the safety of the facility and the radiation protection of the workers involved. EDF takes the necessary steps to control the risks associated with the subcontracted activities and regularly updates them. EDF has thus reinforced the preparation of reactor outages, more particularly to guarantee the availability of human and material resources. 2.5.2 – Assessment of maintenance and subcontracted activities Maintenance of the installations The maintenance of nuclear power plants is subject to regular checks. In 2025, ASNR considers that the overall situation has remained fairly satisfactory, while stressing the importance of EDF continuing its efforts to remedy the difficulties encountered and strengthen quality control of maintenance activities in the long term. In this respect, ASNR has noted from its inspections that the facilities are generally well maintained, and that reactor outage are well managed. However, ASNR considers that EDF must continue to improve the preparation of maintenance activities. Several significant events and inspections highlighted shortcomings in the preparation or execution of activities. The rate of document integration for maintenance requirements improved in 2025. There is still room for improvement in the quality of operational documentation. Progress is also expected in the quality of end-of-procedure analyses. In addition, on several occasions the inspectors noted shortcomings in the completion of operational documents by maintenance operators. The number of Significant Safety Events (ESS) whose root cause analysis reveals a link with Maintenance Non-Quality (NQM) remained stable in 2025 compared with the previous year, following a decrease since 2022. The main failings at the root of NQMs concern the preparation and quality of files, the monitoring of procedures, as well as training, exercises and mastery of technical practices. Finally, ASNR is still noting difficulties with the management of spare parts, which sometimes lead to maintenance activities being cancelled. There are also major disparities in the way fuel stores are run and storage conditions are respected. Several sites are in difficulty, requiring the implementation of priority corrective actions. The organisation for performance of maintenance Although the planning of maintenance activities has improved significantly at most NPPs, it remains an important issue that ASNR will continue to monitor. ASNR sometimes observes a lack of HIGHLIGHT No. 8 Reactor outages Nuclear power reactors must be periodically shut down, every 12 to 18 months, in order to replace fuel depleted during the electricity production cycle. One third or one quarter of the fuel is thus renewed at each outage. These outages mean that certain parts of the installations which are not accessible during the production phase then become temporarily accessible. EDF therefore takes advantage of these outages to carry out inspections, tests and maintenance operations, as well as modifications to the installation. These outages can be of several types: • Refuelling outage and Maintenance outage: these outages, which last from a few weeks to a few months, are devoted to replacing a part of the fuel and to carrying out a verification and maintenance programme, which is more extensive during a maintenance outage than during a refuelling outage. • Ten-yearly outage: this is an outage involving a programme of in-depth verification and maintenance. This type of outage, which lasts several months and takes place every ten years, enables the licensee to carry out large-scale operations such as the complete inspection and hydraulic testing of the reactor coolant system, hydrotesting of the containment or incorporation of design changes resulting from the periodic safety reviews. These outages are scheduled and prepared by the licensee several months in advance. ASNR checks the steps taken by the licensee to ensure the safety of the facility, environmental protection and radiation protection of the workers during the outage, as well as the safety of the reactor for the next production cycle. In the light of the provisions of its resolution 2014-DC-0444 of 15 July 2014 concerning PWR outages and restarts, the monitoring performed by ASNR involves spot-checks. These mainly concern the activities with the most significant safety implications, as well as the processing of any unforeseen events. It consists of on-site inspections and documentary checks, throughout the duration of the outage and in particular prior to restart of the reactor. It is after this inspection that ASNR may or may not approve reactor restart. ASNR Report on the state of nuclear safety and radiation protection in France in 2025 297 01 05 02 06 03 07 04 08 09 10 11 13 12 A / Z
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