French regulator expects to report soon on EPR 'anomaly'

Areva's proposed methodology to demonstrate the strength of the reactor vessel of the EPR under construction at Flamanville is "acceptable", according to a letter French nuclear regulator published on its website yesterday. The ASN (Autorité de Sûreté Nucléaire) referred to the recommendations  a group of nuclear pressure equipment specialists (GP ESPN) had made following a meeting with the regulator on 30 September.

Representatives of HCTISN (Haut comité pour la transparence et l’information sur la sécurité nucléaire) and l’ANCCLI (l’Association Nationale des Comités et Commissions Locales d’Information), as well as foreign safety authorities involved in construction of the unit, attended the meeting as observers.

Areva informed the ASN of its proposed methodology to justify the adequacy of the mechanical properties of the RPV material in May.

The previous month, the French engineering group said that anomalies had been identified in the composition of the steel in certain parts of the reactor vessel. Further tests are planned to show the extent and effect of the areas of the vessel showing higher carbon concentrations. These were seen as potentially high enough to impede the vessel's ability to withstand cracks. Such cracks could, for example, be an unexpected rupture of the upper or bottom heads of the RPV.

Areva conducted chemical and mechanical tests in late 2014 on a vessel head similar to that of the Flamanville EPR. The ASN said in April 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".

The ASN said the experts who met this week have made recommendations outlining other tests Areva could add to its proposed methodology, which by itself would not "restore the guarantee on the first level of defence-in-depth that a technical qualification consistent with current standards would have achieved".

They recommend that Areva includes ways to monitor the operation of the equipment in the final safety case it submits to the ASN.

The regulator said it expects to make a decision on the proposed methodology shortly, adding that it would make its conclusions public soon afterwards.

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 was then expected to start up in 2017.

On 3 September EDF said it has put back the start-up date of the EPR unit by about one year while the cost of the project has now tripled from its original estimate.

Some 98% of the building civil structure has already been completed on the unit as well as 60% of the electromechanical work. However, a new timetable has been drawn up by the company and its partners for the remaining work to complete and commission the 1630 MWe unit.

The new timetable sets out three key milestones, EDF said. Installation of the primary circuit is now scheduled to be completed in the first quarter of 2016, while system performance testing will begin a year later after all electromechanical work has been completed. The loading of fuel and start up of the reactor is now expected to take place in the last quarter of 2018.

EDF said the project costs have now been revised to €10.5 billion ($11.8 billion), up from a December 2012 estimate of €8 billion.

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