EDF / 2018 Reference document

PRESENTATION OF EDF GROUP Description of the Group's activities

Problem of break preclusion and quality deviations in the welds of the main secondary circuit On 30 November 2017, EDF declared a significant event to the Nuclear safety authority regarding the detection of a quality deviation in the welding in the primary secondary pipes that transfer the steam from steam generators to the turbine at Flamanville 3 EPR. The circuit that transfers the steam from the steam generators to the turbine of the Flamanville 3 EPR (main steam line) was designed and manufactured according to the “break preclusion concept”. This approach consists in strengthening requirements for design, manufacture and monitoring in service. These strengthened requirements, requested by EDF, also involve a “high quality” requirement in the building of these circuits. (1) However, these requirements were applied during the design phase but were not correctly taken on board in the welding. Non-compliance with these requirements does not necessarily imply non-compliance with the nuclear pressure equipment regulations. After 21 March 2018, EDF also identified quality deviations on the welding of the pipes of the main secondary system of the Flamanville EPR, during the initial comprehensive inspection. The initial comprehensive inspection, is a regulatory requirement prior to the plant commissioning, which consists, in particular, of examining the welds of the primary and secondary systems. It allows an initial reference inventory of the plant to be conducted before its entry into operation. In accordance with industrial procedures, the welds had been inspected by the consortium of contractors in charge of manufacturing the system. Each weld had been declared compliant by the consortium just as they were being completed. On 10 April 2018 (2) , EDF notified the ASN of a significant event relating to the detection of deviations in the inspection of these welds (part of the main secondary system was already subject to a deviation with respect to the correct application of “break preclusion” requirements). In the second quarter of 2018, EDF thus undertook a new check of all the 150 concerned welds of the main secondary system. Of all the 150 welds checked: 33 welds with quality deviations have to be repaired. Activities to repair the ■ welds with quality deviations started on site at the end of July 2018; EDF also decided to repair 20 welds, even if they did not show any defects, as ■ they were not compliant with the “break preclusion” requirements defined by EDF when the EPR was designed. The remedial action records of the first welds were sent to the ASN and welding started on site in November 2018; For 10 other welds, EDF proposed a specific justification process to the ASN, ■ whereby the high safety level of the facility can be confirmed throughout its operation. After the final analysis, this number was reduced to eight. Furthermore, it appeared after inspection, that one of these eight welds had a small quality defect. The specific justification process mentioned above will be the subject of an in-depth examination by the ASN in the coming months.

Progress of on site implementation The site is still at a high level of activity with close to 3,600 people on site every day. At end-2018, the percentage of assembly of electromechanical equipment was above 98%, with the remaining activity carried out as and when the system performance testing is performed. A number of major milestones were reached in 2018: “cold functional” testing which consists of running several tests including testing ■ for leaks in the primary circuit at a pressure of over 240 bars, higher than its operating pressure; the reactor containment building pressure tests were carried out successfully in ■ April 2018. This is an “in-air” test to verify the proper mechanical behaviour of the concrete structure and its airtightness by increasing the pressure inside the building to six times the atmospheric pressure; the integration of an instrumentation and control configuration representing ■ some 250 changes was completed in early September 2018, and hot functional testing could thus be carried out with a consistent and stable configuration of the instrumentation and control. To date, the three main issues concerning the commissioning of Flamanville 3 are as follows: approval of the strategy for treating the welds of the main secondary circuit, then ■ the success of repair operations, jointly with the main stakeholders: the ASN, partners and their sub-contractors; ramp up of testing in line with safety and quality standards and on schedule so ■ as to be ready by the start date; industrialisation of the finishing off and gradual transfer of the facility to the ■ operator via a new step in the organisation of the site for maximum optimisation of the short-term planning of activities. Quality equipment manufacturing At the end of 2018, most of the equipment of the nuclear section, such as the conventional island, had been delivered and installed on site. The equipment quality situation for the primary cooling system manufactured by Framatome is described below: Reactor vessel In the first half of 2017 the ASN examined “higher-than expected” carbon levels in the vessel head and bottom on the basis of documentation submitted by Framatome, under the supervision of EDF. Based on the opinion on 11 October 2017 of a group of experts appointed by it, the ASN considered the mechanical features of the vessel head and bottom to be up to requirements including in the event of an accident. On 9 October 2018, the ASN authorised: the commissioning of the vessel bottom (contingent on appropriate checks); ■ the commissioning of the vessel head, by limiting the lifespan to 2024, unless the ■ technical feasibility of checks is proven to be similar to the vessel bottom. EDF is currently working on a project to develop the in-service inspection of the vessel head, so as to apply to the ASN in 2019 to keep the current vessel head if this type of operation is industrially feasible. In the absence of such an authorisation, the costs incurred for the manufacture of a replacement vessel head might have to be borne, in part or in full, by EDF. They are not included in the target construction cost due to the fact that they would be incurred, if applicable, after commissioning. Furthermore, an arbitration procedure has been initiated on this matter by EDF against AREVA SA.

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Given that these requirements were stated, the potential for pipes rupturing did not have to be considered during the safety demonstration. This proves, with a high degree of (1) confidence, that accidents are physically impossible or extremely unlikely and that their consequences are limited to acceptable economic conditions. See EDF press release of 10 April 2018 “EDF has detected quality deviations on certain welds of the main secondary system of the Flamanville EPR and has begun additional (2) controls”.

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EDF I Reference Document 2018