ASN has lifted its suspension of the pressure test certificate of a steam generator installed on Fessenheim NPP reactor 2

On 12^th March 2018, ASN lifted its suspension of the pressure test certificate of steam generator N° 335, installed on Fessenheim NPP reactor 2.

After examining the file transmitted by Framatome (formerly Areva NP), ASN considers that the anomaly in the forging of a shell of this steam generator does not compromise its serviceability and that its compliance with the regulations is thus demonstrated. It more specifically notes that the mechanical properties of the material comply with the initial hypotheses of the design studies.

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The Framatome file also relies on controls performed on the steam generator, on the one hand and on chemical analyses and mechanical tests performed on representative scale one replica parts, on the other. These mechanical tests were monitored by an independent organisation. This file was assessed by ASN and its technical support organisation, IRSN. ASN also consulted its advisory committee of experts for nuclear pressure equipment.

On 18^th July 2016, ASN suspended the test certificate it had issued in 2012 for steam generator N° 335, which led to continuation of the shutdown of Fessenheim NPP reactor 2. This suspension followed the detection in 2016 of an irregularity in one of the parts of this steam generator, called the “lower shell”, manufactured by the Creusot Forge plant: the forging process for the lower shell of this steam generator, made in 2008, was not compliant with the technical file submitted to ASN, which had not been informed accordingly at the time.

This decision to lift the pressure test certificate suspension is taken in the light of the safety issues and does not prejudge any legal proceedings which could be taken as a result of the irregularities found in the Creusot Forge plant.