ASN allows longer use of Flamanville EPR vessel head

Areva NP (now Framatome) revealed its discovery of an anomaly in the composition of the steel in certain zones of the reactor pressure vessel's (RPV's) closure head and bottom head of the Flamanville EPR in April 2015. The engineering group initiated a test programme to demonstrate that the mechanical strength of the steel was sufficient in all operating situations, including accident situations. Its conclusions were sent to ASN in December 2016.

In June 2017, ASN said it had provisionally ruled the unit could start up safely, at the end of 2018 as planned, but that the reactor pressure vessel head would need to be replaced once a new one has been produced. Delivery of the replacement lid is scheduled for October 2024.

ASN issued its authorisation in October 2018 for the commissioning and use of the vessel, subject to the implementation of a thermal aging monitoring test programme and on specific controls during the operation. The authorisation was only for the vessel and not the closure head, which ASN said must not be used beyond 2024. At that time, commissioning of the reactor was scheduled for October 2019.

Shortly after EDF announced in December 2022 that fuel loading at the unit had been delayed again until the first quarter of 2024, Framatome requested an extension to the current use-by date of the vessel head. Instead, it asked for the component to be replaced at the end of the reactor's first complete cycle, which has an estimated duration of 15 to 18 months. This first scheduled shutdown is the one during which the first complete requalification of the primary circuit of the reactor is made.

ASN has now agreed to the extension, noting that avoiding a stoppage of the plant during its first cycle to replace the head "will prevent a possible interruption of the reactor start-up tests, avoid the performance of sensitive reactor shutdown and restart operations and reduce the collective exposure related to additional transactions, which constitute elements favorable in terms of nuclear safety and radiation protection".

It added: "The postponement requested by the manufacturer Framatome will lead to a duration of use of the cover of approximately 18 months, ie a shorter period than that envisaged when ASN took its decision of 9 October 2018, which, given the date then envisaged for the start of the reactor, was about four years."

ASN also noted that replacing the vessel head before commissioning the reactor would lead to a further delay of about a year. However, it added: "ASN nevertheless considers that, in the event that the project again experiences a significant delay, the operator must re-examine the possibility of replacing the cover before commissioning the reactor."

The regulator launched a public consultation on 10 March on its proposed decision. That consultation will run until 31 March.

Construction work began in December 2007 on the 1650 MWe unit at the Flamanville site in Normandy - where two reactors have been operating since 1986 and 1987. The dome of the reactor building was put in place in July 2013 and the reactor vessel was installed in January 2014. The reactor was originally expected to start commercial operation in 2013.