EPR Reactor: Information Letter n°15 - ASN monitoring of the EPR Flamanville reactor construction site: notable points.

Published on 25/11/2013 at 11:00

Information notice

In the first half of 2013, ASN continued its monitoring of construction of the Flamanville 3 EPR reactor and various other manufacturing operations for this reactor; ASN carried out several inspections. The notable points observed over these last few months are detailed below.

Verification of the installation of Flamanville 3 reactor dome

Installation of reactor dome

On 16th July 2013, EDF started installing the reactor building dome on the cylindrical structure of the liner. The liner is a metallic envelope covering the interior face of the first containment wall of the building that will house the Flamanville 3 reactor. The function of this envelope is to supplement the sealing of the concrete double-walled containment of the reactor building. It is moreover used as sacrificial formwork during the containment concreting operations.

The 260-tonne metal dome was pre-assembled near the reactor building then hoisted into place using a high-capacity crane. The operations involved moving the dome from its assembly area on the ground some 130 metres from the reactor building, and lifting it onto the jacks placed on the top of the building. These jacks then enabled the dome to be positioned on supports ensuring the necessary space for welding. The fit-up work, carried out with a maximum tolerance of just a few millimetres, lasted until 23rd July 2013; EDF then welded the dome to the liner cylinder during the month of August.

ASN monitored these operations by conducting three site inspections on July 4th and 16th and on August 29th. The purpose of these inspections was to:


  • verify the measures taken by EDF to ensure the availability of the safeguard systems of the Flamanville reactor 2, which is situated in the immediate vicinity of the construction site, assuming that it would be impacted should the crane topple or drop its load;
  • verify that the operations run such that complete sealing of the liner is ensured.


These inspections showed that the prior lifting tests were correctly performed and gave satisfactory results. Furthermore, the teams in charge of operation of the Flamanville reactor 2 were kept regularly informed of how the operations were proceeding and had permanent access to the means necessary to cope with the potential consequences of the crane falling onto its equipment. The inspectors also noted the high standard of EDF's monitoring of the contractors chosen for welding the liner.

ASN is now focusing on monitoring the next stage of construction of the reactor building, namely the concreting of the internal containment wall.

The first nuclear pressure equipment (NPE) installation operations on the Flamanville 3 construction site

In June 2013, ASN set the conditions under which AREVA NP could start a first assembly sequence for the valves and pipes of the safety injection system (RIS) of the Flamanville 3 EPR reactor.

These operations began on 10th June 2013, the first of them involving installing and welding four valves (called "3-way valves") which constitute fixed points from which the other equipment items are assembled.

The 3-way valve with its protective coverings during installation.
The 3-way valve with its protective coverings during installation.

At the beginning of July 2013, AREVA NP informed ASN that the first of these valves had been installed upside down. Further to this error, the ASN-approved inspection body responsible for monitoring these operations suspended performance of the equipment assembly and transfer operations while AREVA NP identified the causes of this deviation and proposed satisfactory corrective measures.

The analysis of the causes of the deviation revealed that it resulted firstly from human and organisational-related factors and secondly from shortcomings in the specification of the requirements applicable to the installation operations and their monitoring.

ASN asked AREVA NP to make the necessary changes in the organisation and the NPE installation documentation. ASN accepted that implementation of these changes be staggered in time, considering that installation of the "three-way" valves could be continued once the documentation had undergone a first modification and on condition that AREVA NP ensures full tracking of the inspections performed.

In early September 2013, AREVA NP proposed ASN a method for identifying and correcting all the shortcomings in the technical documentation used for the first installation sequence, such that each requirement to be met during the operations is correctly specified, with a document certifying the results of the required inspections. This method will also be applied for the subsequent sequences.

ASN considers that the method proposed by AREVA NP allows continuous improvement in the documentation while guaranteeing application of all the associated requirements. ASN thus informed AREVA NP on 24th September 2013 that the first installation sequence operations could be resumed under the surveillance of the approved inspection bodies.

Preparation for operation of the Flamanville-3 reactor

The EDF entity responsible for operation of the future Flamanville-3 EPR reactor, called "Flamanville 3 NPP" currently comprises about 350 employees. The reactor construction activities are supervised by another EDF entity called "Aménagement de Flamanville 3" (Flamanville 3 Development), which is also in charge of the start-up operations. A process is currently underway to gradually transfer responsibility for operation and maintenance of the structures, systems and components from the "Flamanville 3 Development" entity to the "Flamanville 3 NPP" entity in preparation for the commissioning of the reactor. The steps of this process enable the NPP staff to acquire the necessary skills, familiarise themselves with the reactor equipment, produce the operating documentation and develop the appropriate tools.

In this preliminary phase, ASN's oversight of the preparation of the entity tasked with future operation of the reactor is based on two types of action:

  • an annual meeting with senior management of the "Flamanville 3 NPP" entity and its representatives, at which the future licensee presents its review of the preparation for reactor operation over the past year and its prospects for the year to come; these meetings have been held since 2011;
  • on-site inspections specifically dedicated to the Flamanville 3 NPP (one per year between 2010 and 2012 and two scheduled in 2013) on the themes of organisation, the development of skills, production of the operating documentation and transfer of the structures, systems and components

On 4th September 2013 ASN carried out an inspection on the planned organisation for the transfer of the structures, systems and components. ASN concluded from this inspection, which focused on the preparation of the first transfer of one of the reactor safety systems ("safety class"), that the organisation defined and implemented by the Flamanville 3 NPP is satisfactory. More specifically, the NPP staff have developed specific computer aids adapted to the transfer activities and allowing, for example, real-time verifications to be carried out on the ground thanks to the use of tablet computers.

In exercising its oversight, ASN will be particularly attentive to ensuring that the Flamanville 3 NPP personnel take advantage of the best practices implemented in the EDF fleet's facilities and that they gain the best possible grasp of equipment operation during construction of the reactor and the system start-up tests so that they are ready to operate the reactor once commissioned.

Preparation for the installation start-up tests

On 7th May 2013 the ASN Commission signed a resolution[1] that supplements the prescriptions relative to the design and construction of the Flamanville 3 reactor. The main additions brought by this resolution concern the future installation start-up tests which will serve to verify that the as-built installation does indeed conform to the requirements. The complementary prescriptions require EDF to implement a structured approach with the aim of covering in particular:


  • the defining of the start-up tests;
  • the drafting of the documentation necessary for the teams preparing and performing the start-up tests;
  • carrying out the start-up tests;
  • processing the test results and dealing with any deviations discovered during the start-up tests;
  • informing ASN during the start-up tests.


Moreover, certain prescriptions of resolution 2008-DC-0114 have been modified to take into account experience feedback from the construction of EPR reactors since 2008. EDF plans for the first start-up tests on items important for safety to take place at Flamanville 3 by the end of 2013.

Inspections on suppliers' premises

On 19th June 2013 ASN conducted an inspection of the quality and monitoring of the manufacturing activities for the core external instrumentation[2] for the Flamanville-3 EPR reactor; these activities are carried out by AREVA on its Erlangen site (Germany). Further to this inspection, ASN considers that EDF needs to apply greater rigour when validating the specifications proposed by the instrumentation supplier, and must see to the consistency of all the documents describing the characteristics, whether required or obtained, of this instrumentation. This inspection also revealed that some of the manufacturing stages are not monitored with sufficient rigour: certain surveillance activities will therefore have to be repeated so that EDF can decide on the quality of the manufactured instrumentation.

 ASN inspection on the Olkiluoto 3 construction site

On 27th and 28th February 2013, ASN inspectors accompanied by members of IRSN went to Finland within the framework of the regular bilateral relations between the Finnish safety authority (STUK) and ASN devoted to the EPR. During this visit, workshops were organised on various technical themes (start-up tests, nuclear pressure equipment, civil engineering, etc.).

Des inspecteurs de l'ASN en visite en Finlande

The inspectors also used this opportunity to visit the Olkiluoto 3 EPR reactor construction site.

To find out more: (French version)

Refer to resolution 2013-DC-0347relative to the prescriptions for the Flamanville 3 reactor start-up tests

Refer to resolution 2008-DC-0114 resolution 2008-DC-0114 concerning in particular the prescriptions for the design and construction of the Flamanville 3 reactor

Refer to inspection follow-up letter INSSN-CAE-2013-0595 of 22nd July 2013 relative to the inspections of 4th and 16th July 2013 concerning the control of risks during installation of the dome on the inner containment on the EPR construction site

Refer to inspection follow-up letter INSSN-CAE-2013-0868 of 22nd July 2013 of 22nd July 2013 relative to the inspection of 16th July 2013 concerning the control of risks during installation of the dome of the inner containment on Flamanville 1 and 2 NPP

Refer to inspection follow-up letter INSSN-CAE-2013-0604 of 16th September 2013 relative to the inspection of 29th August July 2013 concerning in particular the welding of the dome to the cylinder of the inner containment on the EPR construction site

Refer to inspection follow-up letter INSSN-CAE-2013-0618 of 25th September 2013 relative to the inspection of 4th September 2013 concerning the planned organisation for the transfer of the structures, systems and components within the Flamanville 3 NPP.

Refer to inspection follow-up letter INSSN-DCN-2013-0635 of 28th August 2013 relative to the inspection of 19th June 2013 concerning the manufacture of the core external instrumentation for the Flamanville 3 EPR reactor


[1]Resolution n°2013-DC-0347. This resolution amends and supplements resolution 2008-DC-0114, setting EDF the prescriptions relative to the Flamanville 3 site for the design and construction of the reactor. (French version)

[2] The core external instrumentation system delivers the signals for the core regulation, control, monitoring, limitation and protection functions. The system is designed with three measurement levels in order to cover the full neutron flux range: the source, intermediate and power levels. It is made up of instrumentation channels that measure the neutron flux by means of detectors, and electronic cabinets that supply the instrumentation channels and condition the signals.

Date of last update : 26/11/2021