Deviations on the Flamanville EPR steam lines: the eight penetration welds will have to be repaired

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In a letter of 19 June 2019, ASN informed EDF that, in the light of the numerous deviations in the production of the Flamanville EPR penetration welds, they would have to be repaired.

In 2018, EDF had proposed an approach aiming to justify maintaining these welds as they were. ASN then considered that the outcome of such an approach was uncertain and had asked EDF to begin preparatory operations prior to repair of the welds located between the two walls of the reactor containment [consult information notice published on 03/10/2018].

EDF’s approach was reviewed by ASN, with technical support from IRSN, including consultation of the Advisory Committee for Nuclear Pressure Equipment (GP ESPN) [consult information notice published on 11/04/2019].

In its opinion of 11 April 2019, 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.

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In a letter dated 7 June 2019, EDF asked ASN for its opinion on the possibility of repairing these welds in about 2024, after commissioning of the reactor.In its letter of 19 June, ASN notes that the repair of the penetration welds prior to commissioning of the reactor is technically feasible. Postponement of the repair operations until after reactor commissioning would pose a number of problems, notably with regard to demonstrating the safety of the reactor during the interim period. ASN therefore considers that repair of the welds concerned before commissioning of the reactor is the baseline solution.

To find out more

• Consult the technical notice of 20 June 2019 
• Deviations affecting break preclusion VVP penetration welds on the Flamanville EPR reactor: 2012-2019 time-line  [in french]
• Consult the ASN letter sent to EDF on 19 June 2019