ASN Report 2018

Finally, with regard to fabrication of the fuel assemblies, ASN is continuing its inspections, notably as a result of the anomalies encountered in 2017 on MOX (presence of large sized plutonium-enriched islands) and the fuel cladding (cladding compliance inspection anomalies). EDF’s notification of a significant nuclear safety event concerning the phenomenon of rising neutron flux at the bottom of the fissile column of MOX fuel assemblies, led ASN in 2018 to ask EDF to characterise the loss of the first barrier integrity margin and take compensatory measures pending the deployment of a change to the design of these assemblies. ASN will remain attentive to the deployment and effectiveness of these measures. 2.2  ̶  Nuclear pressure equipment 2.2.1  –  Monitoring of the design and manufacturing conformity of Nuclear Pressure Equipment ASN assesses the compliance with regulatory requirements by the Nuclear Pressure Equipment (NPE) that is most important in terms of safety, said to be “level N1”, which are the reactor pressure vessel, the steam generators, the pressuriser, the reactor coolant pumps, the piping and the control valves and relief valves. These regulatory requirements are a guarantee of their safety. They are defined by a European Directive on Pressure Equipment and supplemented by requirements specific to NPE. This conformity assessment concerns the equipment intended for the new nuclear facilities (more than 200 items are concerned on the Flamanville EPR) and the equipment spares intended for nuclear facilities already in operation (replacement steam generators in particular). For the performance of these duties, ASN can rely on the organisations that it approves, which it can task with performing some of the inspections on the level N1 equipment. They are also responsible for assessing conformity with the regulatory requirements applicable to NPE that is less important for safety, referred to as “level N2 or N3”. Oversight by ASN and its approved organisations comes into play at different stages of design and manufacture of nuclear pressure equipment. It takes the form of examination of the technical documentation for each item of equipment and of inspections in the manufacturers’ facilities as well as in those of their suppliers and subcontractors. Five inspection organisations or bodies are currently approved by ASN to assess ESPN conformity: Apave SA, Asap, Bureau Veritas Exploitation , Vinçotte International and the EDF users inspection entity. Inspection of main primary system welds – Flamanville EPR Analysis of the irregularities detected in the manufacturing files at the Creusot Forge plant for components installed in reactors in service Following the detection of irregularities in certain manufacturing files at the Areva NP Creusot Forge plant in 2016, ASN resolution 2017-DC-0604 of 15 September 2017 ordered EDF to send ASN the review report of the manufacturing files for the components forged by the Creusot Forge plant for each reactor in operation and no later than two months prior to restart following its next refuelling outage. EDF submitted the review report as required by the resolution of 15 September 2017. Certain additional clarifications will be sent to ASN during the course of 2019. The ASN examination of the deviations brought to light by this review, which began in 2017 and continued in 2018, gave rise to additional justification requests but did not reveal any deviation requiring the repair or immediate replacement of an equipment item. Requests were made for subsequent on-site inspections and representative tests to confirm the justifications provided by EDF and the corresponding elements will be examined in 2019. Furthermore, data concerning the castings produced by the foundry on the Le Creusot industrial site, which were requested from EDF by the above-mentioned resolution, will be analysed in 2019. In 2018, ASN finalised the examination of the file concerning the irregularity detected on the lower shell of a steam generator on Fessenheim NPP reactor 2. Following the discovery of this anomaly, ASN suspended the steam generator test certificate on 18 July 2016, the effect of which was to keep this reactor shut down. In July 2017, Areva NP transmitted a file demonstrating the mechanical strength of the component concerned. With the support of IRSN, ASN examined this information which was presented on 27 February 2018 to the Advisory Committee for Nuclear Pressure Equipment (GPESPN). On the basis of the conclusions of the examination, ASN considered that the irregularity affecting the steam generator did not compromise its serviceability and therefore lifted the suspension of the steam generator test certificate on 12 March 2018. ASN report on the state of nuclear safety and radiation protection in France in 2018  281 10 – EDF NUCLEAR POWER PLANTS 10