EPR Reactor: Information Letter n°23: Monitoring the construction of the Flamanville-3 EPR reactor: ASN notable actions in 2020 and 2021
ASN continued its monitoring of the construction of the Flamanville EPR reactor. In 2020 and 2021, it was particularly vigilant regarding the processing of the anomalies detected on the main primary and secondary system welds and the continuation of the reactor start-up tests. ASN also authorised partial commissioning of the installation to allow nuclear fuel to enter the site, starting on 26 October 2020 and ending on 24 June 2021. A look back at these notable events.
Anomalies detected in the main secondary system welds
In 2017, EDF informed ASN of anomalies that had occurred during welding of the main steam letdown pipes (VVP system) of the Flamanville EPR reactor. These pipes are covered by "break preclusion" criteria, which imply tightened design, manufacturing and in-service monitoring requirements such that it can be considered, with a high degree of confidence, that a break of these pipes is extremely improbable. ASN's inspections revealed a lack of proficiency in the welding operations performed on the VVP pipes and deficiencies in EDF's monitoring of its service providers (see EPR Newsletter n° 21).
In reply to the conclusions of the investigations conducted by ASN regarding the anomalies affecting the welds on the main secondary systems presented to the NPE (nuclear pressure equipment) Advisory Committee in April and June 2019, EDF has since 2020 deployed its weld processing strategy (see EPR Newsletter n° 22). The processing strategy adopted for the containment penetration welds consists in complete repair of the welds from the interior using a robot developed by the Westinghouse company. For the other welds on the main steam lines, the processing strategy adopted is also to repair the welds to ensure conformity.
In 2020 ASN, together with the Bureau Veritas exploitation (BVE) organisation, examined the situation prior to the beginning of the first VVP weld repair operations. The first weld repairs were started in the summer of 2020 on the containment penetration welds.
In 2021, the investigations continued and the repair operations were gradually extended to include all the welds that so required, with a repairs completion date currently set by EDF for the end of April 2022.
In addition to the surveillance conducted by the BVE organisation, ASN carries out regular inspections in order to check that the required weld quality is achieved and remains at a satisfactory level, given the increase in the number of repair operations conducted in parallel.
Anomaly on three main primary system nozzles
On 3 March 2021, EDF notified ASN of a significant event concerning a design anomaly on three nozzles of the main primary system of the reactor, the rupture of which is not covered by the reactor’s safety case because their diameter is too large.
The processing solution proposed by EDF is to install a retaining collar around each nozzle concerned. In the event of rupture of the nozzle set-in weld, this collar would limit the size of the resulting break. The consequences of this break would then be covered by the reactor’s existing safety studies.
ASN considered that the solution proposed by EDF is in principle acceptable but will issue a final ruling once EDF has provided the required data concerning the demonstration of the effectiveness of the arrangement, the design, manufacturing and operating requirements applicable to the collars and the quality of the set-in welds around which these collars would be installed.
Anomaly in the post-weld heat treatment of certain welded assemblies
In August 2019 Framatome informed ASN of non-compliance with the required post-weld heat treatment temperatures for certain welded assemblies. Certain welds of the EPR steam generator, pressuriser and main secondary piping are concerned by this phenomenon.
Framatome and EDF submitted elements to ASN supporting, despite this deviation, the possibility of performing the hot tests without jeopardising personnel safety or the integrity of the equipment items concerned.
Their strategy for processing the anomaly affecting the EPR was updated to take account of the residual mechanical stresses generated in the welded assemblies during this processing. This strategy includes repair operations when possible or, failing which, justification that the conformity of the equipment is not compromised. It is in line with the overall strategy for dealing with this anomaly, which also concerns the steam generators on the EDF reactors in service. ASN is currently examining this strategy.
Monitoring the start-up tests
Examination of the results of the start-up tests
Two months before the envisaged date for commissioning of the EPR, EDF is required to communicate the results of the tests performed, in accordance with the binding requirement [INB167-50-1] of resolution 2013-DC-0347 of 7 May 2013. These results include data enabling the validity of the results and the representativeness of the test conditions to be assessed, along with:
- the list of start-up tests still to be performed before commissioning;
- the list of start-up tests already performed and the results of which would not allow commissioning to take place (with the necessary remedial measures).
ASN and EDF have agreed to bring forward the examination of these results on the basis of the tests already performed. Thus, in June 2020, EDF sent ASN a preliminary version of the results of the start-up tests.
Following receipt of this document, ASN put together a two-part investigation programme jointly with IRSN.
The first part of the investigation consists of an examination of the results of the start-up tests submitted in June, plus the corresponding updates which are regularly transmitted by EDF. This examination, which was started at the end of 2020, will continue until commissioning of the installation, in order to incorporate the updates arising from the progress of the start-up tests programme.
The second part of this investigation consists of an examination of several particular technical points. Most of these particular points are anomalies detected during the start-up tests and for which it would appear necessary to conduct an in-depth examination of the solution provided by EDF with a view to commissioning of the installation. A special file is submitted by EDF to ASN for each of the points identified and each file undergoes a specific examination.
These examinations are required before ASN can issue the installation commissioning authorisation, because the start-up tests are able to guarantee the conformity of the installation. Updating of these results is planned for the second half of 2021.
At the same time, ASN is continuing to monitor the start-up tests in progress. In April 2021, it therefore conducted an inspection on the performance of a test requiring the use of radioactive gases, authorised by the installation’s partial commissioning resolution (ASN resolution 2020-DC-0693 of 8 October 2020).
ASN was particularly attentive to monitoring any releases during these tests, along with verification of the pre-requisites (notably the tightness of the systems into which the radioactive tracers were injected).
This inspection showed that the organisation set up by EDF for this first use of radioactive gases within the BNI was satisfactory.
Continued validity of the start-up test results
Given the current delays on the Flamanville EPR reactor construction site, numerous start-up tests were performed well before the scheduled commissioning date envisaged for the installation by EDF. This situation has led EDF to shut down numerous equipment items pending commissioning of the reactor.
The sometimes lengthy period between the tests and commissioning requires that the licensee adopt a strategy to demonstrate that the results of the start-up tests already performed are still valid.
EDF therefore presented a strategy aiming to guarantee the conditions for the long-term conservation of equipment installed on the site. This strategy is currently being evaluated by ASN and its effective implementation is being specifically monitored through a dedicated inspection programme.
In the first half of 2021, ASN in particular conducted an inspection on the conservation of nuclear pressure equipment (NPE). This inspection lasted three days and involved EDF as the NPE licensee, Framatome as the manufacturer, along with the approved organisations APAVE and Bureau Veritas Exploitation. In the second half of 2021, further inspections will concern the conservation of other equipment families (electrical equipment, automation, rotating machines, etc.).
Subsequently, EDF presented a range of processes helping guarantee the continued validity of the test results. This more specifically includes the change monitoring process, the risks analysis process for work on the equipment, the “special systems and means” (DMP) process and the on-site test commissions process aiming to ensure that the test phases as a whole are representative. EDF also adopted a method for identifying additional transverse tests liable to reinforce confidence in the robustness of these processes.
ASN considers that demonstrating the continued validity of the start-up test results is needed in order to prove the conformity of the installation with its baseline requirements, with a view to reactor commissioning. To achieve this, it examines the various processes implemented for performance of the start-up tests and the continued validity of their results, and ensures that they are correctly implemented and effective, by means of targeted inspections.
Review of the quality of the Flamanville 3 reactor equipment
The numerous anomalies identified during the production and inspection of the main secondary system welds, along with the deviations discovered during ASN inspections or addressed as significant events since the start of the project led ASN in 2018 to express the finding of a deficiency in EDF's monitoring of its outside contractors. This finding led ASN to ask EDF to perform a quality review of the Flamanville EPR reactor equipment.
EDF conducted additional inspections as of 2018 through a review programme, which was amended in late 2018 to take account of ASN's request to extend the review to cover a wider range of equipment and subcontractors. In response to ASN’s additional requests made during an inspection on 27 June 2019, EDF changed its programme by adding documentation or equipment inspections. The progress of this programme is periodically presented to ASN and a final report should be transmitted to ASN at the end of 2021.
These additional inspections include the performance of new interpretations of main primary system weld radiographs. These activities were inspected on 21 July 2021, during which the inspectors noted the rigorousness and professionalism of the staff in charge of these inspections, which thus helps provide robust guarantees as to the quality of the production of these welds.
The review of the equipment quality also includes an in-depth examination by EDF of the conformity of the main primary piping with the “break preclusion” baseline requirements. The guarantee of the quality of production of this equipment, required in accordance with this baseline, notably includes the additional inspections currently under way.
Partial commissioning authorisation of the installation for arrival of the fuel
EDF sent an application for partial commissioning of the installation to allow the arrival of fuel on the site, so that the fuel assemblies to be used for future operation could be safely received and stored. This partial commissioning is one of the steps prior to commissioning of the Flamanville EPR reactor, but in no way prejudges this commissioning, which is the subject of a separate examination.
Following the examination of this application, ASN authorised the arrival of nuclear fuel on the Flamanville EPR reactor site, in a resolution dated 8 October 2020, so that it could be stored in the fuel pool until commissioning of the installation.
In order to evaluate the licensee’s preparedness for the fresh fuel reception, handling and pool storage operations after partial commissioning, ASN carried out an inspection on the Flamanville site on 18 and 19 August 2020, ahead of issue of the corresponding authorisation. The checks carried out during this inspection showed that the condition of the installation and the licensee’s level of preparedness were satisfactory for receipt of the fuel on the site.
ASN also carried out an unannounced inspection on 9 November 2020, to check the operating conditions following the arrival on the site of the first fuel assemblies, in particular compliance with the General Operating Rules (RGE) applicable within the context of partial commissioning. ASN also carried out an inspection on 9 December 2020 to check application of the fuel assembly transport rules during receipt on the site. These inspections concluded that appropriate organisations had been defined and implemented for receipt of the fuel assemblies, their handling and their storage on the site.
Incident and accident operations (CIA)
In 2020, ASN carried out an inspection to examine the organisation and resources put into place by Edvance so that, on behalf of EDF, it could draft chapter VI of the General Operating Rules (RGE) devoted to EPR incident and accident operating rules (CIA) and the process for producing CIA documents.
This inspection underlined the high level of expertise and rigorousness on the part of the professionals in charge of each of the subjects, but did reveal several points warranting particular attention concerning the management of changes to CIA procedures.
The inspection also highlighted the primordial role of the simulator in the CIA procedures drafting process, as it is a crucial link in the process to detect anomalies in the CIA operating documents.
On 13 and 14 April 2021, ASN therefore carried out an inspection on the Flamanville EPR reactor to check the preparedness of the operating teams for incident/accident operations (CIA), through work on the simulator and in the installation premises. This inspection mobilised four ASN inspectors and two IRSN experts. ASN underlines the rigorousness and professionalism of the operators during these simulations and considers the level of preparedness of the teams to be satisfactory.
Monitoring of the activities carried out by the suppliers and of surveillance by EDF
ASN performs inspections on EDF’s contractors, for example, equipment manufacturers or holders of contracts for services provided on the construction site. On 7 June 2021, an inspection was therefore performed at Framatome, which is in charge of supplying the software for the Flamanville EPR protection system. This inspection, which followed an inspection on the same topic in January 2020, aimed to assess the quality of production of the software, by checking the correct application of the verification and validation activities, the management of anomalies, the collection and analysis of operating experience feedback, skills management, and EDF’s surveillance of these activities.
Following this examination, the inspectors notably found shortcomings in the application of the development process, raising queries with regard to the quality of the software developed. ASN therefore asked EDF to initiate a detailed analysis of the correct application of the quality plan defining the rules associated with development of the software and to take account of the lessons learned from these findings in the definition of its subsequent surveillance programmes. ASN will monitor the actions undertaken by EDF in response to its requests.
Continued examination of the commissioning authorisation application file (DMES) for Flamanville 3
A new commissioning authorisation application was filed by EDF on 4 June 2021. This application takes the place of the initial application of 19 March 2015 and comprises a complete update of the file appended to the initial application. This file thus contains the safety analysis report, the general operating rules, a waste management study, a decommissioning plan, an on-site emergency plan and an update of the initial impact study with a view to performing an environmental assessment of reactor commissioning.
The examination of the commissioning authorisation application is continuing and primarily aims to ensure:
- that the requests made by ASN are taken into account, notably further to the opinion of the Advisory Committee for Nuclear Reactors (GPR) of 4 and 5 July 2018 on the reactor’s nuclear safety case,
- that the planned level of safety and environmental protection is maintained, notably when processing any anomalies detected.
Certain parts of the fundamental examinations have not been completed, in particular concerning certain aspects of equipment qualification for accident conditions and the general operating rules. This work is receiving very close attention from ASN and is extensively mobilising the EDF teams and the technical experts at IRSN.
ASN is also ensuring that pertinent international experience feedback, notably that from operation of the EPR reactors in Taishan (China) is taken into account.
The reactor commissioning authorisation can only be issued on condition that the overall examination of the file underpinning the application is finalised. In addition, and on this basis, the installation’s conformity with the applicable technical and organisational baseline requirements shall be established, notably by examining the results of the reactor start-up tests and validating the strategy to ensure the continued validity of the start-up test results.
International experience feedback follow-up
ASN participates in several international bodies and regularly organises meetings with the nuclear regulators concerned by the various EPR projects around the world, which enables it to collect feedback on the construction, tests and operation of this reactor. On 12 June, ASN also proposed discussions with its Chinese counterpart, the National Nuclear Safety Administration (NNSA), in order to examine the extent to which the experience feedback from the current operating situation of the Taishan 1 reactor could be considered in the ongoing examination of the commissioning application for the Flamanville EPR. The NNSA responded favourably to ASN’s request and meetings on the subject are continuing.
ASN also regularly checks that EDF satisfactorily incorporates international experience feedback.
To find out more:
Inspection follow-up letters
Date of last update : 09/03/2022