Areva and EDF's program for testing the mechanical properties of Flamanville 3's reactor pressure vessel has been extended. Previously the tests were to be carried out on samples from two forged parts but will now be conducted on three.
The French nuclear regulator - the Autorité de Sûreté Nucléaire (ASN) - released information in April 2015 about the discovery of anomalies in the composition of the steel in certain parts of the reactor vessel of the EPR under construction at Flamanville. Chemical and mechanical tests were conducted by Areva in late 2014 on a vessel head similar to that of the Flamanville EPR. 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". Both affected components - the vessel head and the vessel bottom - were manufactured at Areva's Chalon/Saint-Marcel plant in France.
|A cutaway of an EPR reactor vessel (Image: ASN)
Initial analyses conducted on two parts similar to those at Flamanville 3 showed the "carbon segregation phenomena extend beyond mid-thickness on one of them".
Last December, the ASN said it considered Areva's proposed testing program for the Flamanville 3 vessel to be "acceptable in principle" and had no objections to the start of the new series of mechanical and chemical tests. Under those tests, material sampling and related tests were extended to three-quarters of the thickness of each of the two parts.
In a joint statement, Areva and EDF yesterday said they proposed to the ASN that the testing program be extended to include a third part "to strengthen the robustness of the demonstration". The ASN had approved this addition to the testing program, they said.
The companies noted that the changes will double the number of samples to be analysed in the tests. A total of 1200 material samples will now be taken to "consolidate the representative nature of the three forged parts tested", they said.
The testing program will run until the end of 2016, when a final report will be submitted by Areva and EDF to ASN.
The results of the testing program will be an essential consideration for ASN in its decision-making about the fitness for service of the affected components, the regulator said earlier.
Construction work began on the 1650 MWe unit at the Flamanville site in Normandy 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 late 2018.
Researched and written
by World Nuclear News