ASN Report 2020

means and external mobile means planned for all the installations on a site beyond their initial design basis. Given the nature of the works requested, the licensee must carry out studies for the design, construction and installation of new equipment which first of all require time and secondly a schedule to optimise their implementation on each NPP. Indeed, insofar as these major works are carried out on nuclear sites which are in service, it is also necessary to ensure that their performance does not degrade the safety of the NPPs. In 2015, EDF completed the deployment of temporary or mobile measures to enhance how the main situations of total loss of the heat sink or electrical power supplies are addressed. More particularly, connection means were installed so that, in the event of an emergency, the mobile systems can be connected to provide water. Furthermore, the FARN, which is one of the main emergency management means, was set up. Since 31 December 2015, the FARN teams have had the capacity for simultaneous intervention on all the reactors of a site in less than 24 hours (up to six reactors in the case of the Gravelines site). These provisions are in response to the recommendations resulting from the European peer review in April 2012 as part of the European stress tests. EDF has also started the deployment of certain permanent resources robustly designed and organised with regard to extreme hazards in order to deal with the main situations of loss of heat sink or of electrical power supplies, beyond the safety baselines currently in force, and with core melt accidents. The most important measures are: ∙ installation of a large-capacity Ultimate Backup Diesel- generator set (DUS), requiring the construction of a dedicated building to house it. Owing to the industrial difficulties encountered by EDF in the construction, unforeseen events during the commissioning tests and difficulties arising from the specific measures implemented to limit the spread of the Covid‑19 pandemic, ASN decided in 2019, and then in 2020, to modify the deadlines for commissioning of these DUS. In parallel with this rescheduling, with the deadline now being pushed back to 28 December 2021, ASN issued binding requirements for an increase in the robustness of the existing electricity sources. At the end of 2020, 54 of the 56 DUS had been commissioned by EDF; ∙ the creation of an ultimate water source. On 31 December 2020, EDF installed the ultimate water sources for Flamanville reactors 1 and 2, Bugey reactor 2 and Tricastin reactor 1. EDF also initiated the installation of those for the other sites and intends to complete the works between 2021 and 2023, depending on the sites; ∙ construction on each site of a local emergency centre capable of withstanding extreme external hazards (functionally indepen­ dent in an emergency situation). In 2019, EDF completed the construction of the local emergency centre on the Flamanville site and commissioned it in 2020. For the other sites, EDF plans completion of the works between 2022 and 2026, depending on the site. These measures will also be supplemented during the periodic safety reviews by implementation of the “hardened safety core”. These resources were partially deployed on the Tricastin NPP reactor 1 and on the Bugey NPP reactor 2, during their fourth ten-yearly inspections. The most important measures are: ∙ addition of a new makeup pump to the primary system; ∙ completion of connection by fixed backup water supply systems for the SG and ultimate water make-up for the fuel storage pool; ∙ installation of an ultimate instrumentation & control system and the definitive instrumentation of the “hardened safety core”; ∙ the installation of an ultimate containment cooling system, to prevent opening of the filtered vent on this containment in the event of a severe accident; ∙ the adoption of measures to stabilise the corium on the basemat, in the event of an accident with core melt and reactor vessel melt-through. With a view to implementation of the “hardened safety core”, ASN is examining the design hypotheses for the material provisions and checking that the solutions proposed by EDF can meet the safety objectives set. On the basis of the files transmitted by EDF and the studies carried out, ASN asked the GPR for its opinion on the more important points of these files. 2.10  Continued operation of the Nuclear Power Plants 2.10.1 The age of the Nuclear Power Plants The NPPs currently in service in France were built over a relatively short period of time: 45 nuclear power reactors representing nearly 50,000MWe, or three-quarters of the power output by all the French nuclear power reactors, were commissioned between 1980 and 1990, and seven reactors, representing 10,000MWe, between 1991 and 2000. In December 2019, the average age of the 56 reactors in operation, calculated from the dates of first divergence, can be broken down as follows: ∙ 38 years for the 32 nuclear power reactors of 900 MWe; ∙ 33 years for the 20 nuclear power reactors of 1,300 MWe; ∙ 23 years for the four nuclear power reactors of 1,450 MWe. 2.10.2 The periodic safety review The principle of the periodic safety review The periodic safety reviews of nuclear power reactors comprise the following two parts: ∙ A check on the condition and conformity of the facility: this step aims to assess the situation of the facility with respect to the rules applicable to it. It is based on a range of inspections and tests in addition to those performed in real- time. These verifications may comprise checks on the initial design studies as well as field inspections of the equipment, or even ten-yearly tests such as the containment hydrotests. Any deviations detected during these investigations are then restored to conformity within a time-frame commensurate with their potential consequences. Ageing management is also incorporated into this part of the review. ∙ The safety reassessment: this step aims to improve the level of safety, notably taking account of the experience acquired during operation, changing knowledge, the requirements applicable to the more recent facilities and international best practices. Following these reassessment studies, EDF identifies the changes it intends to make to its facilities in order to enhance safety. The review process for the EDF nuclear power reactors In order to fully benefit from the standardisation of the nuclear power reactors operated by EDF, these two parts of the periodic safety review are first of all covered by a generic studies programme for a given type of reactor (900MWe, 1,300MWe or 1,450MWe reactors). The results of this programme are then applied to each nuclear power reactor on the occasion of its periodic safety review. EDF more particularly carries out a large part of the checks and modifications related to the periodic safety reviews during the ten-yearly inspections of its reactors. ASN Report on the state of nuclear safety and radiation protection in France in 2020 311 10 – THE EDF NUCLEAR POWER PLANTS 10