Note related to the examination of fitness to service of the vessel bottom and cover of the Flamanville EPR reactor. Pedagogical sheet: Analysis of consequences of the fabrication anomaly of the Flamanville EPR reactor vessel bottom and cover

After having recalled the context related to the discovery of a fabrication anomaly in the chemical composition of the steel used in the central part of the vessel cover and bottom of the Flamanville EPR reactor, this report presents the approach proposed and adopted by Areva for the justification of the mechanical strength of the vessel cover and bottom. It indicates the main conclusions of the IRSN and ASN on various issues addressed by the audit performed by AREVA: fabrication controls, material characterisation, thermal-mechanical loadings, mechanical analysis of a risk of sudden failure. The next part proposes a pedagogical sheet of consequences of a fabrication anomaly: presentation of vessel structure and specificities, report of the discovery of this anomaly and main consequence (steel embrittlement), expertise approach, expertise conclusions (control of the absence of any deleterious defect, characterisation of material mechanical properties, assessment of thermal-mechanical loadings, assessment of a risk of sudden failure, and in-service follow-up)