Flamanville EPR reactor: welding flaws not detected during manufacture ASN carried out an inspection on 10th April 2018
On 10th April 2018, ASN carried out an inspection on the Flamanville EPR reactor construction site to examine how the welds on the main secondary systems were checked following EDF’s discovery of welding flaws, which had not been detected during the manufacturing checks.
The inspection revealed that the organisation and working conditions during the manufacturing completion checks were on the whole prejudicial to the quality of the checks. Inappropriate surveillance of this work by EDF and Framatome also failed to identify and remedy the difficulties being experienced by the operators. Certain flaws are still being investigated, in order to understand why they were not detected during the manufacturing completion inspections.
The inspectors consider that the procedures for the performance of the new checks on these welds by EDF are appropriate. ASN does however consider that EDF should propose that these checks be extended to other systems. ASN will issue a position statement on the corrective measures proposed by EDF, notably in the light of the results of the checks which will be sent to it next month.
At the end of March 2018, ASN was informed by EDF that flaws had been detected in certain welds on the Flamanville EPR reactor, which had not been identified by the manufacturing completion inspections.
As part of the “pre-service inspection” prior to commissioning, stipulated by the nuclear pressure equipment regulations, checks were carried out by EDF on the Flamanville EPR reactor main secondary systems welds.
These checks, which were started in March 2018, revealed flaws in the welds which had not been detected during the manufacturing completion inspections performed by subcontractors of Framatome.
In addition, the main steam letdown lines for which deviations from the “break preclusion” requirements had been identified, are also concerned by these manufacturing flaws. These pipes, which constitute a part of the main secondary systems, are thus the subject of the overall inspections initiated by EDF.
To find out more:
Consult the follow-up letter (in french)
 The main secondary systems comprise the secondary containment of the steam generators as well as the pipes and accessories which cannot be safely isolated from it.
 These inspections are mainly performed by means of ultrasounds and radiography.