EPR Reactor: Information Letter n°20: ASN actions for monitoring the Flamanville EPR reactor construction site: significant points for 2017 and early 2018

Published on 03/05/2018 at 16:30

Information notice

View on the EPR Flamanville 3 site from the cliff © EDF Médiathèque - Alexis Morin - Antoine Soubigou / all rights reserved

ASN continued its monitoring of the Flamanville 3 EPR reactor construction site and the various manufactured items intended for it. The significant points for 2017 and early 2018 are detailed below; ASN was particularly vigilant with regard to start-up testing activities, which were ramped up during the course of the past year.

The ASN monitoring work carried out in 2017 more particularly highlighted several points requiring particular attention and which led ASN to call the EDF and Framatome senior management to a hearing on 7th February 2018 concerning the Flamanville EPR reactor project[1].

During this hearing, the ASN Commission more specifically questioned EDF and Framatome on the anomalies affecting nuclear pressure equipment, the reactor start-up tests and the technical investigations in progress relating to the installation’s commissioning authorisation application.

Deviations detected during welding and weld checks on the main secondary systems

At the beginning of 2017, ASN was informed by EDF that the reinforced requirements associated with the “break preclusion” approach had not been passed on to the subcontractor in charge of carrying out 8 welds in its factory for the main steam letdown lines. An ASN on-site inspection on 21st February 2017 revealed that these requirements had also not been taken into account for the welds carried out in the installation itself. EDF’s analysis of this deviation, at ASN’s request, revealed that a number of these welds failed to comply with some of these requirements. ASN is currently continuing its investigation of these deviations and notably carried out another on-site inspection on 27th and 28th February 2018. ASN considers that the organisation defined and implemented by EDF for production of the main steam letdown lines would appear to be inadequate.

In parallel with this investigation, ASN was informed by EDF at the end of March 2018 that flaws had been found in certain welds on the main secondary systems, including several welds on the main steam letdown lines. These flaws had not been identified during the manufacturing completion checks. On 10th April 2108, an ASN inspection revealed that the organisation and working conditions during the manufacturing completion checks were on the whole prejudicial to the quality of these checks. Moreover, inappropriate surveillance of this work by EDF and Framatome also failed to identify and remedy the difficulties being encountered by the operators. ASN will continue to investigate these deviations in the coming months and will be particularly attentive to the quality and results of the new checks implemented by EDF on the welds concerned. ASN considers that EDF should extend these checks to other systems.

Monitoring of the Flamanville 3 EPR reactor start-up tests

ASN continued its monitoring of the preparation for and performance of the EPR reactor start-up tests, which were the subject of seven inspections in 2017, including five that were unannounced. These activities have been intensified, notably with the beginning of the complete systems tests. The inspectors more particularly examined the rigorousness of the preparation for and performance of the tests, the documentation and the processing of any deviations detected, the monitoring of outside contractors as well as the organisation put into place by EDF for the decision on whether to continue with the general start-up tests programme.

In the light of these spotchecks on the testing documentation and on the performance of the activities on the construction site, ASN considers that there is room for improvement in the organisation defined and implemented on the site with regard to the start-up tests. EDF must improve its rigorousness in the preparation for and performance of the start-up tests, by demonstrating that those tests for which procedures have been adapted are indeed representative and by providing real-time documentation of any deviations encountered. EDF must also improve ASN information about the progress of these tests and the deviations detected during them. On this point, ASN asked EDF for an action plan and will check its effectiveness.

Monitoring of the preparedness of the EDF teams responsible for future operation of the Flamanville 3 reactor

At the same time, ASN is monitoring the preparedness of the teams responsible for future operation of the Flamanville 3 EPR reactor. The inspectors are checking the definition and gradual implementation of the various operating organisations, the management of personnel skills and the way in which the future operating documentation is to be drafted, in order to ensure that the teams will be ready to fully exercise their responsibilities for the reactor pre-commissioning and then commissioning phases.

In this respect, ASN carried out six inspections in 2017 devoted to preparations for EPR operation. In the light of these spot-checks, ASN considers that the organisations defined and implemented on the site for drafting the operating documentation for the electricity generating sets and ventilation equipment, for safety management, radiation protection of workers, management of hazards and transports, are satisfactory.

However, ASN considers that the organisation defined and implemented on the site to prepare for the arrival and storage of new fuel on the site (partial commissioning of the installation) is not satisfactory. The licensee shall in particular ensure that the following are implemented:

  • rigorous planning, allowing a definition of precise milestones with targets to be met for commissioning and operation of the nuclear materials storage facility;
  • an action plan for updating the documentation associated with the corresponding partial commissioning application currently being examined by ASN.

Finally, ASN considers that before partial commissioning and commissioning of the reactor, considerable work is still to be done to prepare the teams responsible for future operation of the Flamanville 3 EPR reactor. ASN will continue its monitoring in this field to ensure that the teams responsible for future operation of the Flamanville 3 EPR reactor are capable of fully exercising their responsibility as nuclear licensee during these phases.

Discovery of legacy waste

In May 2016, buried waste was discovered on the Flamanville EPR construction site during work to repair the rainwater drainage network. According to EDF’s initial observations, this waste was neither radioactive nor hazardous as defined by the regulations and primarily consisted of construction materials (concrete, wood, metal pipes, cables). The markings found on certain waste suggest that it had been buried at the time of construction of Flamanville reactors 1 and 2 in the 1980s.

After informing ASN, EDF undertook measures to remove this waste for shipment to a non-hazardous waste disposal facility. As this work progressed, it became apparent that the volume of waste exceeded initial estimates and that some waste did not meet the regulation criteria currently defining non-hazardous waste. EDF thus sent this waste to appropriate disposal routes. ASN carried out an inspection to check the excavation activities in July 2016.

At the beginning of August 2017, EDF informed ASN that oversuits traditionally used in a nuclear controlled area, most of which were packaged in bags, had been discovered among the waste. Initial radiation checks carried out with mobile means proved to be negative. Detailed analyses then revealed the presence of traces of cobalt 60 at the limit of the measuring instruments’ detection threshold. Following this discovery, which resulted in EDF notifying a significant event in August 2017, the waste removal operations were suspended at the request of ASN, pending additional information. EDF thus carried out a soil diagnostic and produced a soil management file (waste and soil). This information was necessary in order to comply with the requirements of the regulations and ASN Guide N°24 concerning the management of contaminated soils so that the waste excavation, sorting and disposal activities could resume. This resumption was authorised by ASN on 19th December 2017.

Preservation of equipment from its installation on the construction site until commissioning of the reactor

In addition to the field check performed during the on-site inspections, ASN carries out spot-checks of the deviations detected by EDF and verifies that they are adequately processed.

Given the reactor commissioning times announced by EDF and further to the deviations encountered on the new heat exchangers installed on the construction site, ASN asked EDF to take full account of the lessons learned from the equipment preservation deviations. EDF analysed all the elements supplied by the equipment manufacturer to identify the underlying causes of the corrosion phenomena observed and define appropriate corrective measures. A programme to restore the conformity of these exchangers was thus defined. A programme to check similar equipment at connection to the systems is still being deployed. Finally, EDF specified the methods for conservation of the equipment following system rinsing and implemented them by means of a position notice. ASN examined these methods during an inspection on 28th and 29th June 2017 and will continue its monitoring of the subject in 2018.

ASN considers that EDF must remain vigilant regarding the preservation of the equipment already installed.

Continued examination of the commissioning authorisation application (DMES) file and the partial commissioning authorisation application (DMESp) files for Flamanville 3

ASN is continuing to investigate the commissioning authorisation application file submitted on 19th March 2015. In accordance with Article 20 of Decree 2007-1557, this file contains a safety analysis report, the general operating rules, a study of waste management, a decommissioning plan, an on-site emergency plan and an updated impact assessment. This file was updated on 30th June 2017.

The ongoing technical discussions will lead to a meeting of the Advisory Committee for Reactors (GPR) next July, in order to reach a conclusion on the answers given to the requests made at the previous GPR meetings concerning “organisation and monitoring resources” (June 2015), “severe accidents and level 2 probabilistic safety assessments” (October 2015), “the safety of fuel handling and storage” (March 2016), “accident studies” (June-July 2016) and “systems and hazards” (December 2016).

At the same time, ASN is examining two partial commissioning authorisation applications: one concerning tests using steam containing tritium as part of the preparations for hot testing, the other concerning the acceptance of fuel assemblies.



[1] Consult the information notice published by ASN on 28rd February 2018 and the position statement letters on break preclusion of the main steam letdown lines and monitoring  of the start-up tests.

Date of last update : 26/11/2021