2.5.2 Assessment of maintenance and subcontracted activities Maintenance of the installations Maintenance is also subject to regular checks by ASN during its inspections in the NPPs. The organisation in the NPPs for largescale maintenance operations was relatively satisfactory in 2023. In this respect, through its inspections, ASN found that the various sites did on the whole deploy the maintenance policy changes initiated by EDF as of 2016. However, ASN finds that the considerable industrial workload on some sites is sometimes an obstacle to the implementation of these changes. In addition, there are still areas for improvement, such as addressing various hazards, preparing activities and the monitoring of activities entrusted to outside contractors. In 2023, spares management also remains a source of shortcomings in the management of the activities. Incorrectly applied national EDF documents or incorrect operational documents are also the cause of inappropriate maintenance operations or maintenance quality defects. In 2022, ASN had found several anomalies concerning inspection programmes performed for maintenance of certain equipment (self-blocking devices, anchors). These anomalies sometimes led EDF to initiate complete programmes for new inspections on certain reactors. After the initial delay in implementation of these programmes, it should be noted that in 2023 improvements were observed in their implementation, even if some difficulties persist. Finally, there were still a large number of significant events arising from maintenance non-quality, undetected by monitoring or by the first level analyses. In this respect, ASN observes that the requalification tests are not always able to detect equipment defects following maintenance or modification work. ASN considers that it is important for EDF to continue with its efforts to remedy the difficulties encountered and improve the quality of its maintenance activities. The organisation for performance of maintenance ASN notes that there are still problems of coordination with the other disciplines and project teams. With regard to maintenance activities, problems of coordination between the various departments were found on a number of sites, with underperforming organisations for the management of several activities at the same time. Management of subcontracted activities ASN checks the conditions surrounding the preparation for (schedule, required human resources, etc.) and performance of the subcontracted activities (relations with the licensee, monitoring by the licensee, etc.). It also checks that the workers involved have the means needed (tools, operating documentation, etc.) to perform their tasks, in particular when these means are made available by EDF. A number of improvements were observed in 2023 in quality management of subcontracted activities. However, there are still difficulties regarding the quality of the monitoring provided (inappropriate monitoring plans, monitoring overly focused on quality assurance and safety rules, to the detriment of actual technical operations, contractors lacking certain required skills, etc.). ASN’s inspections also show a very positive move within the NPPs to improve the skills of the contractors. EDF is implementing tangible measures, such as the increase in the provision of spaces for preparation work on a mock-up. 2.5.3 Regulation of the conformity of facilities with the applicable requirements Maintaining the conformity of the facilities with their design, construction and operating requirements is a major issue insofar as this conformity is essential for ensuring compliance with the safety case. The processes employed by the licensee, notably during reactor outages, contribute to maintaining the conformity of the facilities. The identification and processing of deviations The checks initiated by EDF within the framework of its operating baseline requirements and the additional verifications requested by ASN, on the basis more particularly of operating experience feedback, can lead to the detection of deviations from the defined requirements, which must then be processed. These deviations can have a variety of origins: design problems, construction errors, insufficient expertise in maintenance work, deterioration through ageing, organisational shortcomings, etc. The steps taken to detect and correct deviations, specified in the Order of 7 February 2012, play an essential role in maintaining the level of safety of the facilities. The nuclear power reactors must be periodically shut down for replacement of the 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. They are thus put to good use by EDF to carry out checks, tests and maintenance, as well as to perform works on the facility. These refuelling outages can be of several types: • Refuelling Outage and Maintenance Outage: these outages, which last a few weeks, 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 major operations such as a complete inspection and hydro-testing of the primary system, hydro-testing of the containment or incorporation of design changes resulting from the periodic reassessments. These outages are scheduled and prepared by the licensee several months in advance. ASN 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. Pursuant to the provisions of resolution 2014-DC-0444 of 15 July 2014 relative to PWR outages and restarts, ASN performs 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, for the duration of the outage and in particular prior to restart of the reactor. It is after this inspection that ASN may or may not approve reactor restart. REACTOR OUTAGES 306 ASN Report on the state of nuclear safety and radiation protection in France in 2023 • 10 • The EDF Nuclear Power Plants
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