Flamanville EPR vessel anomalies under scrutiny

Anomalies have been identified in the composition of the steel in certain parts of the reactor vessel of the EPR under construction at Flamanville, Areva has informed the French nuclear regulator. Further tests are planned to show the extent and effect of the areas of the vessel showing higher carbon concentrations.

Anomalies have been identified in the composition of the steel in certain parts of the reactor vessel of the EPR under construction at Flamanville, Areva has informed the French nuclear regulator. Further tests are planned to show the extent and effect of the areas of the vessel showing higher carbon concentrations.

Areva conducted chemical and mechanical tests in late 2014 on a vessel head similar to that of the Flamanville EPR. The French nuclear regulator, the ASN (Autorité de Sûreté Nucléaire), said today it had been informed that these test results "revealed the presence of a zone in which there was a high carbon concentration, leading to lower than expected mechanical toughness values".

A cutaway of an EPR reactor vessel (Image: ASN)

"Initial measurements confirmed the presence of this anomaly in the reactor vessel head and reactor vessel bottom head of the Flamanville EPR," ASN said. Both forged steel components were manufactured at Areva's Chalon/Saint-Marcel plant.

Areva and EDF have proposed to ASN that a new series of tests is conducted on a representative vessel head "in order to precisely identify the location of the zone concerned and its mechanical properties." The companies said that those new tests are already underway.

ASN said it will decide "on the acceptability of the test program, check its correct performance and examine the file to be submitted by Areva to demonstrate the robustness of the Flamanville EPR reactor vessel." The regulator noted that it will call on the services of its technical support organization, the Institute for Radiological Protection and Nuclear Safety (IRSN), and the Advisory Committee of Experts for Nuclear Pressure Equipment.

EDF and Areva said that its teams are "working to perform the additional tests as soon as possible, following approval by the ASN on the test conditions, and to provide the safety authority with the necessary information to demonstrate the safety and quality of the corresponding equipment. In parallel, work continues at the Flamanville EPR."

Construction work began on the 1650 MWe unit at the Normandy site in December 2007. EDF is architect engineer of the project, while Areva is contributing the nuclear steam supply system and Bouygues Construction is leading the civil engineering consortium. The dome of the reactor building was put in place in mid-July 2013 and the reactor vessel was installed in January 2014. The reactor was originally expected to start commercial operation in 2013, but due to delays is now expected to start up in 2017.

ASN said it has informed its foreign counterparts who are involved in the construction of EPR units.

EPRs are also under construction at Olkiluoto 3 in Finland and Taishan 1 and 2 in China. Olkiluoto 3 has been under construction since 2005 and has seen several revisions to its start-up date, which is now expected by 2018. Taishan 1, which has been under construction since 2009, is expected to start up in 2016, while Taishan 2 is scheduled to begin operating a year later.

Researched and written
by World Nuclear News