SATISFACTORY DEPLOYMENT OF THE STRESS CORROSION TREATMENT STRATEGY Following the discovery of stress corrosion cracking on the safety injection system of the main primary systems of some reactors at the end of 2021, EDF proposed a strategy involving the systematic replacement in 2023 of the lines considered to be susceptible to the phenomenon on those reactors liable to be the most severely affected, with inspection of all reactors by 2025. In 2023, EDF implemented the proposed replacement strategy. The inspections carried out revealed the fact that certain weld repair processes during manufacturing were a factor liable to influence the appearance of stress corrosion, even on lines considered not to be susceptible to the problem. This enabled EDF to revise its inspection strategy, giving priority to the welds which had been repaired during manufacturing. EDF also decided to extend its spot-check inspection programme to all stainless steel lines connected to the primary system. ASN considered this strategy to be appropriate, while pointing out that it might need to be revised in the light of the lessons learned from the ongoing programme of investigations. ASN also asked EDF to already take account of these lessons in the design of new reactors. ASN is working in close collaboration with its foreign counterparts on this subject. Following the presentation of the findings made in France on the EDF fleet, the Western European Nuclear Regulators’ Association (WENRA) issued recommendations concerning monitoring of the stress corrosion phenomenon for the reactors in operation, along with prevention of this phenomenon at the design stage. PRESSURE ON THE “FUEL CYCLE” FACILITIES IS EASING BUT THIS SHOULD NOT MASK THE NEED TO PREPARE FOR THE FUTURE The pressure identified in recent years in the “fuel cycle” eased in 2023, in particular due to improved Melox plant production. These improvements and the prospect of a new Multi- year Energy Programme (PPE) could lead to the saturation time-frame for the Orano pools at La Hague being reconsidered. ASN nonetheless considers that new safe storage capacity will eventually be needed, in compliance with current standards, to ensure margins to deal with any contingencies affecting the facilities. Generally speaking, ASN considers that the entire chain of back-end fuel management facilities and units must urgently be made more resilient so that the 2040 target set in the current PPE can be reached in safe conditions. This entails measures to be implemented without delay in order to meet this target, such as consolidation of MOX fuel production, developing interoperability between the reprocessing lines, the performance of considerable renovation and safety improvement works identified during the periodic safety reviews. The work undertaken on densification of the existing pools at the La Hague plant, along with dry storage, as means of dealing with the saturation risk, shall be continued. ASN FINALISES THE TECHNICAL EXAMINATION PROCESS AND CHECKS THE LICENSEE’S PREPAREDNESS FOR EPR COMMISSIONING The year 2023 was devoted to finalising the examination of technical subjects still open (design of primary system safety valves and performance of the internal water tank filtration system in particular), incorporating the latest modifications, and the performance of hot tests to ensure the overall qualification of the installation. In May 2023, ASN carried out an in-depth inspection involving a large number of inspectors and experts, to check the licensee’s preparedness for commissioning of the installation. ASN noted that the overall level of preparedness was good but it did underline that significant work was still required to ensure that the operational documentation was available and had been assimilated by the operating and maintenance personnel. In 2023, ASN continued with its technical examination of certain topics, notably those linked to Operating Experience Feedback (OEF) from EPR reactors abroad, as well as the conformity assessments of the nuclear pressure equipment. THE EPR 2 PROGRAMME MUST TAKE ADVANTAGE OF LESSONS LEARNED FROM THE EPR In August 2023, EDF submitted the creation authorisation application for two EPR 2 reactors in Penly, for which the safety options had been the subject of an ASN opinion in 2019. The Penly reactors are the first ones in the EPR 2 programme, the aim of which is to incorporate the lessons learned from the design, construction and operation of the EPR reactors in France and abroad, along with feedback from operation of the existing reactors. The lessons learned by ASN and the French Institute for Radiation Protection and Nuclear Safety (IRSN) on the Flamanville EPR project led to reinforced oversight being adopted for the examination of the creation authorisation application. ASN and the IRSN defined their examination strategy, identifying the schedule, 4 ASN Report on the state of nuclear safety and radiation protection in France in 2023 Editorial by the Commission
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