No immediate action required on components, says EDF

18 September 2019

In-service steam generators affected by non-compliance in a stress-relieving heat-treatment process are safe to continue in use, French utility EDF said today. Investigations into the deviation at Framatome's Saint-Marcel site are ongoing.

Installation of one of the affected steam generators at the Flamanville 3 EPR (Image: EDF)

On 9 September, EDF informed France's nuclear safety regulator, the Autorité de Sûreté Nucléaire (ASN), of its initial investigations concerning the deviation in certain nuclear-related components produced at the Saint-Marcel site in France.

According to EDF, Framatome's majority owner, the non-compliance concerned an excursion from temperature ranges in certain areas during manufacturing operations, specifically involving detensioning heat treatment on some steam generator welds and pressuriser seals.

EDF and Framatome have now said they have identified 16 steam generators affected by the deviation which have been installed at six operating reactor units: Blayais 3 and 4, Bugey 3, Dampierre 4, Fessenheim 2 and Paluel 2.

EDF said: "At this stage of the technical investigations being carried out on these components, EDF believes that the observed deviations do not adversely affect the components' fitness for service and do not require immediate action."

In a separate statement, Framatome confirmed the investigations "confirm at this stage that the mechanical integrity of the components is not called into question."

The components that are not yet in service include four steam generators and the pressuriser that have been installed at the EPR under construction at Flamanville 3. In addition are three replacement steam generators that have been delivered to Gravelines units 5 and 6, but have not yet been installed.

EDF and Framatome said they are continuing their technical investigations "with extreme diligence" and will keep ASN informed on a regular basis.

The specific stress-relieving heat treatment process is not being used while the investigations are being completed, but other production activities at the Saint-Marcel site are not affected, Framatome said last week.

The Saint-Marcel site, in Saône-et-Loire, assembles the heavy equipment for the primary loop of nuclear reactors, including vessels, steam generators and pressurisers. Since its establishment in 1975, the plant has supplied components for 106 nuclear reactors worldwide, according to company information.

Framatome is owned by EDF (75.5%), Mitsubishi Heavy Industries (19.5%) and Assystem (5%).

Researched and written by World Nuclear News