Information notice No.5: ASN keeps a close watch on construction work on the future Flamanville 3 reactor
During the last quarter of 2008, ASN continued its inspection activities on the construction site of the Flamanville 3 EPR. Highlights of this work included:
Manufacturing of the liner (metal lining designed to seal the containment)
ASN carried out several inspections of liner welds in the Flamanville 3 EPR reactor building. These inspections revealed:
- 1. deviations from liner technical requirements concerning, in particular, the welding methods used, the climatic conditions during welding operations and the welding data package available to welders,
- 2. inadequacies in the application of the Order of 10 August 1984 relating to the quality of the design, construction and operation of basic nuclear installations, particularly with respect to the qualification of the liner pre-manufacturing shop on the Flamanville 3 site, monitoring of welding operations and non-destructive testing of welds and, lastly, the quality management system of the company responsible for liner welding.
ASN considered that the high rate of repair on some welds was an indication that liner welding conditions were not adequately controlled. It consequently asked EDF to demonstrate that the liner could guarantee containment safety under such conditions and, if necessary, propose additional tests and inspections.
In the meantime, ASN asked EDF on 12 December 2008, to suspend any irreversible operations that would be incompatible with additional weld inspections.
On 4 February 2009, following an in-depth examination of the supporting material provided by EDF and after consulting the IRSN, ASN asked EDF to take the following steps:
For welds already completed:
- provide additional data to that already transmitted, in particular concerning tests to be carried out on welds representative of those found on the site,
- inspect 100% of certain types of weld. ASN considers that the proposals already submitted by EDF for the other welds will avoid any impact on the liner's containment function.
For future welds:
- submit an action plan aimed at making a significant improvement to the quality of these welds, with a monthly report on the actual implementation of the plan, and make an assessment of its effectiveness after 6 months' application on site,
- inspect 100% of welds until a significant improvement in their quality has been confirmed.
Reinforcement operations (rebars)
Following the recurring defects in concrete reinforcement operations reported during the first six months of 2008 on the Flamanville 3 site (see information letters 2, 3 and 4), ASN asked EDF on 17 June 2008 to implement an action plan to remedy this problem.
During their inspection on 17 December 2008, ASN inspectors appraised the effectiveness of the plan and noted an improvement in the quality of performance and more stringent technical inspections of concrete reinforcement work.
Sea outfall tunnel
During the last quarter of 2008, EDF informed ASN that it had encountered some technical difficulties in the construction of the sea outfall structure. It also reported a change in the methods used to excavate the outfall tunnel. Given the change made to the path originally planned for the sea outfall tunnel and the use of a tunnel boring machine, ASN asked EDF to check the analysis of safety risks for reactor no. 2 of the Flamanville NPP (possible impact of mine blasting operations and vibrations induced by the excavation work, checking that the mass of rock does not suffer any deformation, etc.).
Essential service water system piping at the pumping station
The essential service water system works with an intermediate cooling system to cool the safety-related equipment of the future reactor. Following the ASN inspection on 2 July 2008, EDF carried out some additional investigations resulting in the scrapping of certain pipes that were not up to production standards.
ASN considers that EDF has taken adequate steps as far as the safety of these pipes is concerned.
In 2004, ASN and its technical support agency, the IRSN, decided to work more closely with the Finnish Nuclear Safety Authority (STUK) to pool available feedback concerning inspection work on the construction of EPRs on the Olkiluoto site in Finland and the Flamanville site in France. This closer cooperation is based on periodic meetings, mutual alerts and joint visits.
Within this context, three ASN inspectors accompanied by three IRSN agents, visited the Olkiluoto 3 site in Finland on 14-15 January 2009. The visit provided an opportunity to exchange information and points of view on the detailed design of concrete structural work on the reactors and to compare practices. During the visit, the French team was invited to observe an inspection performed by an STUK team.