Welding of the main steam transfer pipes of the Flamanville 3 EPR reactor: ASN defines the conditions for resuming certain on-site welding operations
ASN has informed EDF of the conditions for resuming certain welding operations on the main steam transfer pipes of the Flamanville EPR reactor. The welding operations involved are restricted to those performed using the "TIG orbital" process which enables high mechanical performance to be achieved.
These pipes have been the subject of design and production deviations about which ASN communicated on 23rd February and 11th April 2018.
On the basis of the inspections already carried out on these pipes, EDF asked for the opinion of ASN before resuming certain welding operations using the TIG orbital process on the main steam transfer pipes.
ASN considers that the mechanical properties of the welds obtained with this process make it possible to envisage resuming the welding operations under certain conditions. ASN requires EDF to put in place an organisation and means of monitoring that will prevent recurrence of the observed deviations. EDF will also have to demonstrate that these welding operations do meet the requirements of the break preclusion baseline.
Starting of these operations remains subject to ASN approval.
 TIG orbital welding is an arc welding process using a non-consumable electrode. TIG is an acronym for Tungsten Inert Gas. Tungsten refers to the electrode and Inert Gas is the type of plasmagenic gas used. The arc is created between the electrode and the part to weld with gas shielding. The arc rotates continuously at least 360° around a fixed part (such as a tube).