EPR Reactor: Information Letter n°9: Despite delays at the worksite, ASN has maintained the same pace of inspection as in 2009.

During the second quarter of 2010, ASN continued its inspection activities at the Flamanville 3 EPR construction site.

ASN describes requirements for liner manufacture

Leaktightness of the EPR reactor building is assured by the presence of a leaktight metal barrier, or liner, inside the double concrete containment. On 23 June 2010, EDF informed ASN of an increase in the number of faults detected in a weld in the liner. Amid recurrent concerns over the issue, ASN inspectors paid a visit on 7 July 2010 to validate measures implemented by EDF to improve weld quality.

In 2008 and 2009, following observations made during inspections at the Flamanville 3 site, ASN requested EDF to implement an action plan to improve quality of liner welds and, while awaiting convincing results, to perform radiographic testing on all welds. The action plan specified rules for welding conditions and training for welders.

During their visit on 7 July 2010, ASN inspectors observed that the ergonomics of the welding position of the horizontal weld in question was the primary cause of the new problems. They also observed that radiographic testing was not performed as welding work advanced: the delay in performing an inspection prevented quick detection of inferior weld quality. On the day of the inspection, EDF had already temporarily suspended new welding activity, reminded those concerned of the 2009 action plan and begun radiographic testing of all questionable welding. Repair of areas showing faults has now been completed.

Welding difficulties caused by the ergonomics of the welder’s post had already been identified as one of the main causes of the 2008-2009 events. ASN also determined that EDF’s treatment of the anomalies detected in 2008 and 2009 was not performed correctly and requested that EDF apply this operating feedback to all welding activities at the site. ASN however wishes to emphasize EDF’s proactive response in implementing preventive measures following detection of the deviation in June 2010.

Important safety-related event at Flamanville 2 reactor

On 8 June 2010, a worker at the Flamanville 3 worksite partially pierced a concrete block containing one of the 400 kV electric cables supplying the auxiliary transformer [1] of reactor 2 at the Flamanville nuclear power plant. EDF’s monitoring of activities led to a quick halt to drilling in progress. On the same day, reactor 2 operators observed a reduction in oil pressure in the electric cable, an indication of degradation.

At the time of the incident, reactor 2 was shut down for refueling, with nuclear fuel unloaded and sufficient emergency electrical supply for this condition. The event was classified level 0 on the INES scale. Detailed analysis of the event is under way, with lack of information for construction site workers and poor identification of the cable in the area cited as preliminary causes.

Since 2005, and later during each specific stage of the worksite, EDF has identified and analysed risks from the Flamanville 3 site for the two reactors in operation to define and implement countermeasures to assure there are no safety consequences for these reactors. After analysis, ASN took decisions to control major risks prior to construction. ASN regularly performs inspections at the Flamanville 3 site and the nuclear power plant in operation at Flamanville to verify that measures implemented by EDF regarding these risks are in compliance with ASN’s instructions.

Inspections at component suppliers

In 2009 and 2010, ASN performed several inspections on suppliers of equipment used for building the Flamanville 3 reactor. The inspections are intended to verify that EDF tests and monitors these activities in accordance with the requirements of the order of 10 August 1984 for assuring a high level of quality in manufacture and facility safety.

ASN has carried out two inspections on EDF’s testing and monitoring of equipment suppliers since the start of 2010, the first one at a supplier of tanks and pools for the reactor and fuel buildings on 20 April 2010 and the second at a pump manufacturer on 1 June 2010. The inspections led to follow-up letters that can be found on ASN’s website.

The inspections concluded that there is room for improvement in EDF’s EPR Flamanville 3 project organisation, especially with regard to monitoring by EDF and validation of the list of activities concerned by quality. Nevertheless, the organisation of firms responsible for manufacturing is satisfactory overall with regard to the requirements in the order of 10 August 1984.

Flamanville 3 reactor instrumentation and control (I&C) system

In order to improve the robustness of the I&C system of the EPR reactor, ASN asked EDF to modify one of the reactor’s control platforms. EDF had already considered this modification in late 2009 in response to ASN’s request of 15 October 2009.

On 15 October 2009, ASN informed EDF that safety of equipment constituting part of the Flamanville 3 EPR reactor I&C (SPPA T2000 platform) had not been demonstrated. It requested EDF to provide additional supporting evidence and examine alternative design measures.

EDF has since worked hard to comply with ASN’s requests. Its initial response and additional substantiation were sent to ASN beginning in late 2009.

The Flamanville 3 EPR I&C system comprises two related platforms:

• Téléperm XS, specifically developed for the nuclear industry and designed to protect the reactor during incidents or accidents;

• SPPA T2000, a conventional component used for functions associated with normal reactor operation and certain functions designed to protect the reactor during incidents or accidents.

After ASN and IRSN, its technical support agency, examined the initial information provided by EDF, ASN informed EDF in a letter dated 9 July 2010 that the ability of the SPPA T2000 platform to accommodate certain reactor protection functions remained to be demonstrated. ASN therefore asked EDF to modify the SPPA T2000 platform in order to improve its robustness and make it compatible with EPR-type reactors. This modification consists of duplicating some reactor protection functions assigned to the SPPA T2000 on the Téléperm XS platform.

So that ASN may complete examination of I&C system documentation, EDF will submit detailed information about design improvement and its impact on the reactor safety demonstration to ASN before the end of 2010.

[1] Each reactor is supplied by two outside electrical lines from the national grid and two emergency diesel generators. In normal operation, electrical energy to a reactor is supplied by a step-down transformer connected to the main line. In case of a failure on the main grid, the reactor is supplied by the auxiliary transformer connected on the auxiliary line.