4. Regulation and oversight of reactor projects The EPR2 reactor EDF is developing a new reactor, called “EPR2”. It aims to incorporate the lessons learned from the design, construction and commissioning of the EPR reactors and OEF from operation of existing reactors. As with the EPR reactors, this project aims to meet the general safety objectives of third-generation reactors. Furthermore, this reactor will integrate all the lessons learned from the Fukushima Daiichi NPP accident, as of the design stage. This more specifically entails reinforcing the design against natural hazards and consolidating the independence of the installation and the site in an accident situation (with or without core melt) until such time as the off-site resources can intervene. ASN examined the Safety Options Dossier (DOS) for this reactor project, with the support of IRSN, taking account of the recommendations of Guide No. 22 on PWR design. On 16 July 2019, ASN thus published its opinion on the proposed safety options. ASN considers that the general safety objectives, the baseline safety requirements and the main design options are on the whole satisfactory. ASN’s opinion identifies the subjects to be considered in greater depth prior to submitting a reactor creation authorisation application. Additional justifications were in particular needed on the break preclusion approach for the main primary and secondary piping, the approach for dealing with hazards, fire and explosion in particular, and the design choices for certain safety systems. The justifications required were specified by ASN in a letter sent to EDF in July 2021. Further to ASN’s opinion, EDF changed its break preclusion approach for the main primary and secondary systems piping. EDF intends to make a number of design, manufacturing and organisational changes to enhance safety. These changes will more particularly concern the choice of materials and manufacturing and inspection techniques. Furthermore, even though EDF applies a break preclusion approach, it also intends to add certain devices to mitigate the consequences of any break, such as separating walls, whip-restraint devices and steam evacuation vents. ASN considers that, given the additional measures, using a break preclusion approach for the main lines of the primary and secondary systems of the EPR2 reactor project is acceptable. This position statement, issued in September 2021, supplements ASN’s 2019 opinion on the safety options for this reactor project. In April 2021, ASN also issued a position statement on the additional information provided by EDF regarding a military aircraft crash. ASN considers that the EDF approach would be able to achieve safety objectives for the EPR2 reactor identical to those of the Flamanville EPR reactor. In February 2021, EDF sent ASN a preliminary version of the safety analysis report for advance examination, were a construction programme for new reactors actually to be launched. A file examination programme was drawn up jointly with IRSN. ASN is also examining the safety options dossiers for the main nuclear pressure equipment. ASN issued opinions concerning the reactor vessel in 2021 and the SGs in 2022. In 2022, with the support of the IRSN, ASN also examined the baseline requirements for application of the break preclusion approach, which concerns equipment said to be “non-rupturable components” (vessel, SG, pressuriser, reactor coolant pump volutes) as well as the EPR2 reactor main primary and secondary system lines. Examination of the break preclusion baseline requirements continued in 2022 and will be presented to the GPESPN for its opinion in 2023. WELDS ON LINES OF THE MAIN SECONDARY SYSTEMS OF THE FLAMANVILLE EPR REACTOR Major repairs are required to 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. After examining these intervention means and the qualification of the processes in 2020, ASN inspected the production of these eight welds in 2021. The post-weld heat treatment and final weld inspections were performed in 2022. These welds comply with the break preclusion requirements. Most of the other welds on the main steam lines which are to be repaired, of which there are about 50, are located in an environment with no access difficulties. In 2022, as in 2021, ASN continued to assess the conditions for their repair and to monitor the weld repair operations. EDF was attentive to ensuring that the number of repairs made at the same time is compatible with the organisation of worksite surveillance. This work should continue in 2023, in particular with regard to the post-weld heat treatment and non-destructive inspection activities. At the same time, EDF analysed the quality of other welds, in particular those on the SG feedwater lines. This work led EDF to decide to repair ten or so additional welds. EDF’s treatment strategy was considered by ASN to be appropriate. Implementation of the orbital TIG process – weld on the main secondary system ASN Report on the state of nuclear safety and radiation protection in France in 2022 315 • 10 • The EDF Nuclear Power Plants 10 01 07 08 13 AP 04 06 12 14 03 09 05 11 02
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