2.4.6 Assessment of the risk prevention measures relating to hazards ASN checks that risks linked to hazards in the NPPs are taken into account, notably based on the reassessment of the design of the installations during the periodic safety reviews, analysis of the licensee’s baseline safety requirements, examination of significant events and the inspections performed on the sites. The steps taken to mitigate the risks linked to hazards are regularly inspected by ASN. The Fukushima Daiichi NPP accident led EDF to reinforce its organisation for the management of risks relating to extreme hazards. More specifically, networks of coordinators were set up for all the NPPs to oversee the implementation of the actions defined to deal with these hazards. Annual reviews are also held to improve this organisation. Fire risks Fire risks are significant. ASN thus reminded EDF in 2016 that, for the purposes of the fourth periodic safety review of the 900 MWe reactors, it expected a well-structured and robust safety case based on a “Defence-in-Depth” approach. ASN examined the justification methods produced by EDF, along with the corresponding modifications, and obtained the opinion of the Advisory Committee for Nuclear Reactors (GPR) in 2019. This examination shows that the changes proposed by EDF represented considerable improvements to the safety case (for example, sectorisation resistance studies, taking account of the effect of smoke). In addition, the new methods adopted identified sectorisation aspects for which correct working is particularly important. For example, the fire doors which are required to be closed were identified and will be subject to specific monitoring. On the sites, ASN observes no significant change concerning management of the fire risks, with a number of outbreaks of fire for the year 2021 comparable to that found in 2020, and an appreciably higher number of significant fire-related events. In 2021, ASN ran an enhanced inspections campaign concerning management of fire risks in seven NPPs and asked for corrective measures to remedy the findings made following these inspections, in particular: ∙ the management of equipment stores and warehouses, which represent considerable calorific potential, must be improved. EDF must in particular demonstrate that fire sectorisation is sufficient, in the light of these stores, keep exhaustive inventories and guarantee compliance with the conditions specified for these activities; ∙ the management of sectorisation must also be improved in certain NPPs: ASN sometimes notes that inspections are incomplete, inaccurate information is communicated to the control teams and anomalies are not detected or processed. ASN has observed a number of improvements in the monitoring of fire permits related to the deployment of a new computer application. Fire detection management, equipment maintenance and personnel training are in general satisfactory and, since the end of 2021, ASN notes that the alarm verification officers in all the NPPs have been working in pairs. In 2021, EDF also continued with its measures to improve management of the fire risks in the premises identified as being particularly sensitive to this hazard in the light of the potential consequences for safety. ASN thus considers that the efforts made by the NPPs to take corrective measures, notably the deployment of tools and action plans, must continue and the personnel must receive greater support in this respect and be given the means needed to perform the required actions. Finally, following an ASN request in 2019, EDF in 2021 presented ASN with its guidelines to improve its firefighting organisation, notably by reinforcing the capacity of its response resources to deal with an established fire. In 2022, EDF will define the deployment plan for its new organisation for all the NPPs. Explosion risks ASN checks the explosion risk prevention and monitoring measures, paying particular attention to ensuring that it is taken into account in EDF’s baseline safety requirements and organisation. ASN also ensures compliance with the “EXplosive ATmospheres” (ATEX) regulations to ensure worker protection. The management of explosion risks is not yet satisfactory for all the nuclear reactors. Certain maintenance and inspection work required by EDF’s internal doctrine is not always carried out satisfactorily. Furthermore, ASN observes that the integration of OEF, the processing of certain deviations and the deployment of certain modifications are sometimes postponed and this is not always justified given the potential safety consequences. During inspections, ASN is particularly vigilant to the inspections and corrective measures taken by EDF to guarantee the compatibility of the electrical equipment with use in rooms where an explosive atmosphere is liable to form. ASN notes the efforts made by EDF to reduce these deviations through the implementation of reinforced monitoring and the deployment of action plans leading to equipment replacement. Furthermore, in 2021, EDF worked on updating documents concerning protection against explosions, required by the regulations concerning the risks involved in the formation of ATEX and conducted conformity audits on the equipment concerned. EDF also changed its personnel training programme regarding explosion risks and incorporated it into the regularly held exercises on the explosion topic. ASN considers that EDF must continue to pay particular attention to this subject and ensure that the explosion risk prevention approach is implemented with all necessary rigour on all the sites. Internal flooding risks Considerable efforts are required on most sites to improve control of the internal flooding risk, in particular with respect to: ∙ the maintenance of the necessary equipment (piping, floor drains, etc.); ∙ the risk assessments during maintenance operations and in the event of detection of a malfunction of a necessary equipment item; ∙ the compliance with the corrective action deadlines identified by the annual reviews; ∙ the training of the coordinators and awareness-raising among the EDF and contractor personnel. In 2019, ASN thus sent requests to EDF asking it to supplement the approach adopted for improved control of the internal flooding risk, to ensure the correct operation of the floor drains, to reinforce maintenance of the piping liable to lead to internal flooding and to ensure improved management of their ageing. In response to these requests, EDF implemented improvement measures. In addition, EDF has initiated field visits 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 its 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. ASN Report on the state of nuclear safety and radiation protection in France in 2021 293 10 – THE EDF NUCLEAR POWER PLANTS 08 07 13 04 10 06 12 14 03 09 05 11 02 AP 01
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