Results

Nuclear Safety Authority of the French Republic

05/21/2019 | Press release | Distributed by Public on 05/21/2019 03:45

Information Letter No.21

ASN continued its monitoring of the Flamanville 3 EPR reactor construction site and the various manufactured items intended for it. The significant points in 2018 and early 2019 are detailed below; ASN was particularly vigilant with regard to the processing of the deviations detected on the main secondary system welds and the continuation of the reactor start-up tests.

Deviations detected during performance and inspection of welds on the main secondary systems

At the beginning of 2017, EDF informed ASN of deviations that had occurred during welding of the main steam transfer pipes (VVP system) of the Flamanville EPR reactor. These pipes are concerned by a 'break preclusion' approach, which implies tightened design, manufacturing and in-service monitoring requirements such as to consider that a break of these pipes is extremely improbable, with a high degree of confidence. The consequences of a break on these pipes are therefore not studied in the facility's nuclear safety case.

In order to achieve the expected high standard of manufacturing quality, the licensee (EDF) and the manufacturer (Framatome) have defined tightened requirements, more specifically with respect to the mechanical properties. However, these tightened requirements were not specified to the subcontractor responsible for these welding operations. The inspections carried out during manufacturing showed that the high level of quality resulting from these requirements had not been reached for certain welds.

In addition, in March 2018, during the complete pre-service inspections of these pipes as required by the regulation, EDF identified several production flaws. These flaws should have been detected by the manufacturer on completion of manufacturing. This finding led EDF to implement a new inspection programme for all the welds on the main secondary systems, which includes the VVP pipes. These new examinations, conducted by EDF under ASN supervision, brought to light flaws requiring repair.

All of these deviations and ASN's findings during its inspections revealed a lack of expertise in the welding operations performed on the VVP pipes and shortcomings in EDF monitoring of its contractors.

In July 2018, EDF undertook to repair the welds concerned by the deviations identified, except for the eight welds located between the two containments of the reactor building, for which access is harder.

In December 2018, EDF sent ASN a file aiming to demonstrate that the quality of these eight welds is sufficient and enables their breakage to be precluded with a high level of confidence.

ASN's examination of the EDF file, with the support of IRSN, continued in 2019 with the consultation of the Advisory Committee for nuclear pressure equipment (GP EPSN) on 9 and 10 April 2019, which considered that EDF must repair these eight welds or abandon its break preclusion approach concerning them, by making the necessary reactor modifications to take account of any such breaks in its safety case.

In addition, the identification of shortcomings in EDF's monitoring of its contractors led ASN to ask EDF to conduct a quality review of the Flamanville 3 EPR reactor equipment, extended to include a broader scope of equipment and subcontractors, while adapting the depth of the review to the specific issues concerned.

Authorisation for commissioning and operation of the Flamanville EPR reactor vessel

At the end of 2014, Framatome revealed an anomaly in the chemical composition of the steel used in the Flamanville EPR reactor pressure vessel closure and bottom heads, which could impair its ability to withstand crack propagation.

After ASN issued an opinion on this anomaly in October 2017, Framatome submitted a vessel commissioning and operation authorisation application on 13 July 2018. ASN examined this application, drawing on the conclusions of its 2017 opinion. It also verified compliance with the technical and regulatory requirements other than those concerning the chemical composition of the steel of the reactor vessel closure and bottom heads.

On the basis of the conclusions of this examination and after analysis of the observations of the public collected in September 2018 during the public consultation, ASN authorised the commissioning and operation of the Flamanville EPR reactor pressure vessel on 9 October 2018, subject to the performance of a test programme to monitor thermal ageing, plus specific inspections during operation of the facility. As the current state of knowledge does not enable the feasibility of these inspections to be confirmed for the vessel closure head, ASN set a service life limit at end of 2024 for the existing vessel closure head.

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 2018, including two that were unannounced. These inspections more specifically concerned the performance of the 'functional tests with vessel open' and preparation for the 'hot 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 to decide on whether to continue with the general start-up tests programme.

In the light of this examination, on a test basis, and of their documentation, ASN considers that the organisation of the start-up tests as defined and implemented on the site is on the whole satisfactory. Following ASN's requests, EDF improved the rigorousness of the test documentation and how it informs ASN with regard to the general performance of the tests. EDF must continue its efforts concerning the rigorousness of the preparation for and performance of the start-up tests, by improving its demonstration of the representativeness of the tests for which procedural adaptations are implemented.

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 following the reactor pre-commissioning and then commissioning phases.

In this respect, ASN carried out four inspections in 2018 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 environmental protection, in-service monitoring of pressure equipment, control of the fire risk and operation of the reactor are satisfactory.

However, ASN considers that more particularly in terms of drafting the operations documentation, considerable work is still to be done before commissioning of the reactor, 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.

Monitoring of the Flamanville EPR engineering activities

In 2018, ASN carried out inspections in the EDF engineering departments responsible for the detailed design studies of the Flamanville NPP reactor 3, on the topic of equipment qualification, management of deviations and the modifications to be implemented after commissioning of the installation.

The inspection performed on 5 December 2018, concerning equipment qualification, revealed shortcomings in the processing and lifting of the qualification reservations[1] identified by EDF and its suppliers. These shortcomings, already observed during a previous inspection, led ASN to serve EDF with formal notice to produce and keep proof of qualification of the Flamanville EPR reactor equipment (see ASN decision of 25 February 2019). EDF undertook to comply with the provisions of the 'BNI' order and its proposed measures are considered by ASN to be satisfactory. ASN will periodically check the progress of the action plan implemented by EDF.

Management of legacy waste

Following the discovery in May 2016 of legacy waste on the Flamanville EPR construction site zone (see information notice of 4 September 2017 and Newsletter N°20), EDF undertook a soil diagnostic and produced a land management file (waste and soils) in order to comply with the requirements of the regulations and of ASN Guide N° 24 (in French only) concerning contaminated soil management.

On 19 December 2017, the resumption of waste excavation, sorting and disposal activities was authorised by ASN on a part of the waste area. Owing to the construction site constraints, the soil diagnostic could only be carried out partially and the file was submitted in order to determine the feasibility of waste sorting with a view to reusing the uncontaminated land. This first 'pilot' phase for processing of legacy waste was carried out during the course of 2018. It enabled part of the zone to be treated and successfully demonstrated the feasibility of the envisaged sorting techniques. During this first phase, the rainwater drainage network was also repaired and an oil separator was installed.

Following this first phase, EDF started a second soil diagnosis campaign at the end of 2018, in order to obtain complete data about the legacy waste zone. EDF will then have to submit a land management file (waste and soil).

Continued examination of the commissioning authorisation application file and the partial commissioning authorisation application files for Flamanville 3

ASN is continuing to investigate the commissioning authorisation application file submitted on 19 March 2015. This file contains the 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. It was updated on 30 June 2017.

ASN obtained the opinion of the Advisory Committee for Reactors (GPR) on 4 and 5 July 2018 regarding the Flamanville EPR reactor safety analysis report. This meeting was more particularly devoted to the answers provided at the previous GPR sessions devoted to this reactor since 2015. The Advisory Committee considers that the reactor's safety case is on the whole satisfactory and points out that some additional information is still required concerning how the fire risk is addressed and the behaviour of the fuel rods which have experienced a boiling crisis. The GPR also considers that the design and design basis of the back-up systems and auxiliary safety systems are on the whole satisfactory and observes that additional information is still required concerning the breaches liable to affect the fuel storage pool cooling system.

At the same time, ASN is also examining the partial commissioning authorisation application to enable the fuel assemblies to be received.

Finally, in a decision dated 26 July 2018, ASN authorised the introduction of steam containing tritium into certain reactor systems in order to prepare for and carry out the hot tests. This authorisation required further decisions concerning effluent discharge and monitoring of the Flamanville site environment, which came into force on 7 October 2018.

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[1] Technical points to be resolved before being able to declare qualification of the equipment.