Assessment of nuclear pressure equipment conformity The NPE of the Flamanville reactor includes that making up the main primary and secondary systems presented in points 1.4 and 1.5 (reactor pressure vessel, SG, pressuriser, reactor coolant pumps, piping, safety valves) but also that constituting other parts of the Nuclear Stream Supply Chain System Design (NSSS). During the course of 2023, ASN continued to assess the conformity of the NPE design. The main topics raised by these assessments, along with their conclusions, were presented during sessions of the GPESPN on 20 and 21 June 2023. The subjects relating to repair of the welds on the main steam letdown lines (covered by the break preclusion baseline requirements), and the operations performed on other piping not subject to these requirements, to post-weld heat treatment, or the prevention of SC risks, were presented at these sessions. ASN considered that ultimately these various subjects were dealt with in such a way that it could rule that the equipment concerned was conforming. On some subjects, such as SC, or the coating of certain valves, follow-up work will nonetheless be carried out by EDF during the first years of operation. In addition, several cases of irregularities during equipment manufacturing were reported to ASN. ASN systematically analyses their potential consequences for the safety of the installation. Oversight of construction, start-up tests and preparation for operation In 2023, ASN carried out an inspection campaign on EDF, Framatome, and the organisation it mandated to perform checks, focusing on repair of the secondary systems welds. ASN considers that this work was carried out rigorously, with a good level of monitoring by EDF, leading to confidence that a high level of production quality will be achieved. Oversight of construction has repeatedly revealed faults in construction quality, requiring corrective measures. At ASN’s request, EDF carried out additional checks during an equipment quality review. In 2023, ASN reviewed the results, which confirmed the quality of equipment production and identified areas for improvement to be addressed during the EPR 2 project. Given the numerous scheduling delays, EDF implemented an equipment conservation strategy pending commissioning. The conservation activities were inspected on the site by ASN in 2023, which found that EDF’s strategy was satisfactory in the light of the additional maintenance work performed and the checks conducted on the equipment at the end of the conservation phase. Since 2022, ASN has also initiated a campaign of inspections regarding the completion of the installation, in order to check that EDF is fully cognizant of the activities still to be carried out (end of assembly, modifications, tests, deviations processing, etc.) and has scheduled them prior to commissioning of the reactor. ASN considers that significant work has been done in recent years to obtain a satisfactory level of finishing. It will nonetheless remain vigilant with regard to completion of the remaining activities before commissioning. ASN continued with the examination of the installation startup test results in order to check that the as-built facility complies with the assumptions used in the safety case. This examination will continue in 2024, notably on the basis of the results of the tests to prepare for fuel loading and the reactor startup tests. ASN continued its checks on preparations for operation and notably carried out a five-day in-depth inspection in May 2023, which involved 15 inspectors and 11 IRSN experts. During this inspection, ASN found that the operating organisations were defined and most of them were already in use and the personnel had a good understanding of the installation. ASN nonetheless noted that considerable work was still to be done on the production of operational documentation for the control and maintenance of the installation. In 2024, ASN will carry out a follow-up inspection before commissioning, to ensure that the steps taken in response to its requests have indeed been implemented and meet the objectives set. Overall, in 2023, ASN carried out 10 inspections of EDF on the Flamanville site, including one in-depth inspection on preparation for operation and a tightened inspection on the hot requalification tests, plus three inspections in the engineering departments. ASN also carried out Labour Code inspections. The conclusions of these inspections are presented in the Regional Overview in the introduction to this report. Major repairs were required on the welds on the lines of the main secondary systems of the Flamanville EPR reactor. The majority of these welds are located on the main steam lines, and are subject to a “break preclusion” approach: they thus require mechanical properties and a level of manufacturing quality that are particularly high. Eight of these welds are located in the annulus between the two containment walls of the reactor building. The difficult access conditions required the development of special intervention means and the qualification of specific welding, inspection and heat treatment processes. Most of the other welds on the main steam lines to be repaired, of which there are about fifty, are located in an environment with no access difficulties. At the same time, EDF analysed the quality of other welds, in particular those on the SG feedwater lines. This work led it to make the decision to repair ten or so additional welds. The work done on all of these welds was completed in 2023 with post-weld heat treatment and non-destructive tests, as well as the performance of hydraulic testing. This last step is the key step in the final verification of these repair activities. ASN carried out checks at each step in these repairs, with the support of an approved organisation. WELDS ON THE SECONDARY SYSTEMS OF THE FLAMANVILLE EPR REACTOR 318 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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