NOTABLE EVENTS 2023 external hazards. This design only required very minor changes to take account of the lessons learned from the accident at the Fukushima Daiichi Nuclear Power Plant (NPP – Japan). DIFFICULTIES ENCOUNTERED DURING MANUFACTURE OF EQUIPMENT AND CONSTRUCTION OF THE REACTOR ASN carried out nearly 600 inspections during construction of the EPR reactor. These inspections were primarily carried out on the Flamanville site, within the EDF head office departments and in the manufacturing plants. ASN thus checked the activities involved in civil engineering, manufacturing and equipment assembly, installation testing and preparation for operations. ASN also carried out labour inspectorate duties on the construction site. Throughout the project, ASN carried out its oversight duties and sometimes required that EDF modify its project when the safety issues so warranted. In 2008, a series of anomalies found during concrete pouring and rebar installation led ASN to tell EDF to suspend concrete pouring operations for the safety-important structures. Similarly, in 2011, ASN told EDF to suspend concrete pouring activities on the inner containment as a result of pre-stressing duct positioning anomalies. Between 2015 and 2018, ASN asked EDF for in-depth justification data concerning the reactor vessel, for which there was a manufacturing anomaly in the steel of the bottom head and closure head. Following its examination, ASN considered that this anomaly was not such as to compromise the commissioning of the reactor pressure vessel, provided that specific checks are carried out during operation of the installation. Owing to the difficulties involved in performing these checks on the vessel head, ASN decided to limit its service life and it will have to be replaced. In 2019, ASN considered that the nature and the particularly large number of deviations that occurred at the design stage and during manufacture of the main steam line welds on the containment penetrations represented a major obstacle to maintaining these welds “as is”, and that their repair before commissioning of the reactor should be the reference solution. Finally, a large number of welds on the main secondary system lines had to be repaired. Various irregularities were also brought to light in the equipment manufacturing plants during the course of the project, both in France and abroad. This situation shows that neither the monitoring and inspection chain, nor the high level of quality demanded in the nuclear industry, were able to completely rule out the risk of counterfeit, fraud and falsification. It is notably at the urging of ASN that Framatome, called Areva NP at the time, brought irregularities to light in its Creusot Forge plant in 2016. Each irregularity detected requires that specific investigations be carried out by EDF and its subcontractors. ASN checks the robustness of these investigations by means of technical exchanges and inspections, while sometimes calling in qualified organisations for the purpose of inspections. These verifications concern the causes, the identification of the scope of the irregularities, the action plans implemented, as well as the consequences for equipment conformity and the safety of the facility. ASN oversight is carried out in parallel with any legal action being taken. More generally, ASN asked EDF to carry out an overall review of the quality of the reactor equipment, notably by means of additional checks on the main equipment items with safety implications. The commissioning authorisation will enable EDF to initiate fuel loading into the reactor. EDF will then conduct a programme of tests to verify the reactor’s safety and performance. This is scheduled to last about eight months. This programme was examined by ASN with the support of IRSN. ASN will monitor the performance of the programme, as it will do throughout the operating life of the reactor. Many lessons were learned from the construction of the Flamanville EPR reactor, by both EDF and its suppliers. For its part, ASN adapted its oversight methods for the construction of future reactors (see notable event “The safety challenges for the new nuclear programme”). n ASN Report on the state of nuclear safety and radiation protection in France in 2023 15
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