ASN Report 2017

349 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 12  - EDF Nuclear Power Plants deviations or to take corrective actions as a result of experience feedback could be reduced. During its inspections, ASN also assessed the organisation of the sites for dealing with the explosion risk, including nuclear safety and worker protection aspects in the management of this risk. Despite the steps taken by EDF, management of the explosion risks is not yet satisfactory on all the nuclear reactors. Certain maintenance work and inspections required by EDF’s internal doctrine (nitrogen tightness tests of the double wall of certain pipes carrying hydrogenated fluids, etc.) are not always carried out. Furthermore, the updating of certain documents (periodic test procedures and document concerning protection against explosions), the integration of lessons learned, the handling of certain deviations and the deployment of certain modifications can be postponed, something that cannot always be justified with regard to the potential safety consequences. ASN notes the efforts made by EDF to reduce these deviations through the implementation of reinforced monitoring and deployment of the action plan. However, ASN considers that EDF must continue to pay particular attention to this point and to the application of the regulations concerning the ATEX risk, and ensure that the explosion risks prevention approach is implemented with all necessary rigour on all the sites. The provisions for the prevention and management of the internal flooding risk are also regularly checked by ASN. These inspections show that the steps taken to manage this type of hazard are not up to the level expected for all the sites. ASN more specifically observes that on some sites, the network of coordinators is still being set up and is not fully operational. EDF has initiated walkdowns to identify the piping which could cause internal flooding in the electrical buildings, which are particularly vulnerable to this risk, in order to assess the need to reinforce their maintenance. In accordance with ASN’s requests, EDF will extend these surveys to the other buildings. ASN sees as positive the fact that EDF has initiated the refurbishment of the circuits of certain cooling systems that are particularly susceptible to corrosion. In 2016 and 2017 EDF sent ASN notification of several significant safety events concerning the flow of water caused by leaks from piping in poor condition or valve lock-out errors during maintenance operations. Considerable efforts are required on most sites to improve the management of the flooding risk, in particular with respect to: ཛྷ ཛྷ maintenance of the necessary equipment (piping, floor drains, etc.); ཛྷ ཛྷ risk assessments during maintenance operations and in the event of detection of a malfunction of a necessary equipment item; ཛྷ ཛྷ compliance with the action deadlines identified by the annual reviews; ཛྷ ཛྷ the training of the coordinators and awareness-raising among the EDF and contractor personnel. The operating and maintenance conditions of the seismic detection equipment are considered to be satisfactory. The annual reviews allow the identification of areas for progress and these are on the whole implemented. EDF is however required to continue with its efforts, notably with regard to the training of staff and awareness-raising among contractors. ASN notes that the operating instructions in the event of an earthquake are not always sufficiently operational and that more regular simulations would improve their applicability. In 2017, EDF notified several significant events of level 2 on the INES scale (International Nuclear and Radiological Event Scale, which comprises eight levels from 0 to 7) concerning seismic resistance defects of equipment necessary for managing the safe shutdown of the reactors, cooling of the fuel and containment of radioactive products. The handling of these deviations was frequently checked by ASN (see point 2.4.7). These deviations reveal that EDF must reinforce its management of the conformity of its facilities with the provisions for dealing with an earthquake. The inspections concerning the hazards associated with extreme temperatures show that EDF’s organisation could be improved on the majority of sites. On several sites, ASN more particularly found a lack of forward planning in preparing the facility for the summer or winter configuration. During its inspections ASN repeatedly notes that EDF does not systematically initiate the required measures if certain temperature thresholds are exceeded. These findings led ASN to issue requests for corrective action. The risk assessments associated with the deployment of countermeasures should also be improved. Finally, ASN requires efforts from EDF with regard to the training of its staff and awareness-raising FOCUS Leaktightness flaw in the penetrations necessary for managing an internal flood The integration of the operating experience feedback from the internal flooding that occurred on the Le Blayais (2012) and Fessenheim (2014) reactors led EDF to initiate an inspection campaign on the penetrations (openings in the walls for running cables or piping between two areas) on all its reactors. EDF found numerous leaktightness flaws in the penetrations of the electrical buildings. These deviations stem primarily from poor incorporation of the baseline requirements concerning internal flooding and fire into the databases used to draw up the maintenance programmes. These deviations were the subject of a generic significant safety event notification in 2015 and led to the drafting of a programme to monitor and restore the conformity of the databases and penetrations in all the reactor buildings in operation. In 2016, ASN submitted several requests more particularly concerning the extension and forward planning of these checks. Following the inspections carried out in 2017, ASN considers that the methods for processing this deviation in the electrical buildings of the 900 MWe reactors are appropriate. ASN will remain vigilant in the coming years with regard to the complete handling of this deviation.