ASN convened its Advisory Committee concerning the deviations detected in welds on the main steam transfer pipes of the Flamanville EPR reactor

On 9 and 10 April 2019, ASN convened its Advisory Committee

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or Nuclear Pressure Equipment (GP ESPN) concerning the approach proposed by EDF to deal with the deviations detected in welds on the main steam transfer pipes of the Flamanville EPR reactor. Representatives from the Flamanville CLI, the HCTISN, the ANCCLI and foreign safety regulators concerned by the construction of an EPR reactor attended this session as observers.

These welds are affected by design and production anomalies. In its letter of 2 October 2018, ASN considered that priority should be given to restoring their conformity and asked EDF to send it a file presenting its deviation processing approach. This file was examined by the ASN nuclear pressure equipment department, with the technical support of IRSN and their conclusions were presented to the GP ESPN.

The GP ESPN sent ASN an opinion concerning the eight welds situated on containment penetrations. ASN is publishing this opinion, along with the report from its nuclear pressure equipment department, which was presented to the GP ESPN.

The GP ESPN notably considered that the nature and particularly high number of deviations in the design and production of these welds were major obstacles to the application of a break preclusion approach. It was therefore considered that EDF should repair these eight welds and bring them into conformity or abandon the break preclusion approach concerning them by making modifications to the reactor enabling such breaks to be covered by its safety case.

On the basis of this opinion, ASN will shortly be issuing a position statement on the approach proposed by EDF.

The GP ESPN was unable to examine the information concerning the other main steam line welds, for which EDF intends to carry out work to restore conformity. It will meet again on 6 June 2019 to examine EDF’s proposals.