EPR Reactor: Information Letter n°8: ASN continues inspections on the EPR Flamanville reactor construction site

The French Nuclear Safety Authority (ASN) continued its inspections on the EPR Flamanville reactor construction site during the first quarter of 2010, and found work to be progressing in good order. Several issues are noteworthy.

Reactor Building prestressing sheaths positioning anomaly

The EPR Reactor Building containment is formed of two containment walls with a space between them. There is an inner wall made of prestressed concrete [1] and an outer wall made of reinforced concrete. The inner containment wall has an internal liner made of steel. This whole assembly ensures that radioactive substances are contained under normal and accident conditions and protects the reactor from external hazards. The functions of the inner containment wall require certain conditions [2] to be complied with in construction.

During its inspections in 2008 and 2009, the ASN examined the prestressing system four times. Specifically, the ASN asked EDF to ensure that the procedures for installing the prestressing accessories complied with the relevant requirements. At the time of the inspection on 18 November 2009, before pouring the first concreting lift for the inner containment wall, EDF reported to the ASN inspectors that the position of the prestressing sheaths within the reinforcements for the Reactor Building inner containment wall were outside the tolerances. EDF turned to its design and engineering department for their opinion and decided to leave the sheaths as they were and pour the concrete for this lift.

Following the ASN’s request, EDF forwarded a fuller subsequent demonstration proving that this non-compliance with required tolerances was not detrimental. This report is currently being studied by the ASN. At the ASN’s request, and as laid down in rule INB167-51, instituted by ASN decision No. 2008-DC-0114 of 26 September 2008, the ASN must from now on be informed of all subsequent concreting lifts for the inner containment wall. This will enable the ASN to make spot-checks and check beforehand that EDF has implemented provisions to prevent the repeat of anomalies, and to check subsequently the measurements made after the concrete is poured.

Start of mechanical assembly installation activities

New activities began at the Flamanville 3 construction site during the second half of 2009 and in early 2010. While civil engineering construction activities continue, mechanical assembly work is being carried out (installation of supports, piping, tanks etc.), with ever increasing numbers of on-site workers. The ASN’s inspections have been adapted to take into

account these new activities.

The interactions between this assembly work and the civil engineering work was covered in various inspections in 2009 and 2010, because any incorrect positioning of the mounting devices built into the structure of the buildings may have consequences on the work carried out by the mechanical assembly teams to position their components.

In addition, the ASN's inspections on 6 November 2009 and 24 February 2010 focused on the organisational

methods used by EDF to monitor these assembly activities – traceability and consistency between documents, management of deviations from the documentary reference framework, cleanliness management, storage conditions, incorporation of feedback relating to difficulties encountered in manufacturing the liner.

These initial inspections demonstrated to the ASN that the organisational methods used to monitor these activities was, on the whole, appropriate. However, the ASN noted that cleanliness requirements were not always complied with on site, and that particular care needs to be taken in this area.

Inspections by and reporting to the Reactor Safety Advisory Committee

The ASN draws on the opinions and recommendations of a standing committee of experts whenever it is preparing to make its most important decisions.

The reactor safety advisory committee will be asked to examine the application for commissioning [3] the Flamanville 3 reactor. The advisory committee will also issue its opinion on highly sensitive issues prior to commissioning. In 2009, for instance, the reactor safety advisory committee issued an opinion on the general architecture of the instrumentation & control systems for the future reactor at Flamanville 3. The ASN has suggested using dedicated annual meetings to inform the advisory committee of the actions implemented by the ASN and the French Institute for Radiological Protection and Nuclear Safety (IRSN), in order to prepare the committee for these various demands. A meeting was held on 18 March 2010, after the initial information meeting had taken place on 7 May 2009. The most recent meeting gave the opportunity to present reactor safety advisory committee members with a progress report on the Flamanville 3 project (construction, design, manufacturing and qualifications) and on the inspections carried out by the ASN and IRSN. Prior to the information meeting, the advisory committee visited the Flamanville 3 reactor construction site on 8 March 2010. Committee members were accompanied by various ASN staff members, including the regional manager from ASN Caen, in order to gain an understanding of the on-site construction activities.

The ASN draws on the opinions and recommendations of standing committees of experts when it is preparing to make its most important safety-related decisions.

In 2009, for instance, the reactor safety advisory committee issued an opinion on the general architecture of the instrumentation & control systems for the future reactor at Flamanville 3. The committee will be asked to examine the application for commissioning [3] the Flamanville 3 reactor.

In order to prepare itself for the requests that will be made, the reactor safety advisory committee visited the Flamanville 3 reactor construction site on 8 March 2010 and attended a meeting on 18 March 2010, at which a progress report was presented to committee members on the Flamanville 3 project (construction, design, manufacturing and qualifications) and on the inspections carried out by the ASN and IRSN.

Joint inspection by ASN with the Finnish authority STUK of AREVA NP’s supplier that is responsible for Flamanville 3 reactor coolant system manufacturing operations

On 29 and 30 March 2010, the ASN and Finnish safety authority STUK jointly inspected Fives Nordon at its Nancy site. Fives Nordon is AREVA NP’s supplier that is responsible for Flamanville 3 reactor coolant system manufacturing operations. The purpose of the inspection was to examine actions implemented following the detection of deviations in the manufacture of reactor coolant pipes for the Olkiluoto 3 EPR project in Finland. The letter issued following this inspection has been published on the ASN website www.asn.fr.

The ASN inspectors deemed that implementation of the action plan proposed by AREVA NP and its supplier to correct the cause of the deviations detected was not sufficient to allow the manufacture of equipment for the Flamanville 3 EPR project to begin. The inspectors requested information regarding the quality of the risk analysis, the implementation of a system of internal inspections, the formalisation of quality-related actions and a detailed plan for implementing requirements relating to the quality system and manufacturing framework. After examination of this information, the ASN subsequently allowed manufacture to resume.

[1] Prestressing is a construction technique for improving the mechanical strength of a structure. For a nuclear reactor, it involves tensioning steel cables that run through sheaths that are embedded in the concrete.

[2] These requirements are formally laid out in the design and construction rules for the EPR reactor civil engineering works (referred to as ETC-C or EPR technical code for civil works).

[3] Commissioning of the Flamanville 3 reactor, during which radioactive substances are introduced into the facility, is subject to ASN authorisation in accordance with Article 20 of French Decree No. 2007-1557 of 2 November 2007.