The review process for the EDF nuclear power reactors In order to benefit from the standardisation of its nuclear power reactors, EDF first of all implements a review of the provisions common to all the reactors of a given type (900 MWe, 1,300 MWe or 1,450 MWe reactors). The results of this programme are then applied to each of them 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. In accordance with the provisions of Article L. 593-19 of the Environment Code, following this periodic safety review, the licensee sends ASN a periodic safety review concluding report. In this report, the licensee states its position on the conformity of its facility and details the modifications made to remedy deviations observed or to improve the safety of the facility and, as necessary, specifies the additional improvements that it will be making. ASN analysis ASN examines the periodic safety reviews in several stages. It first of all issues a position statement on the objectives of the review and the guidelines of the generic programmes to verify the state of the facility and the safety reassessment proposed by EDF, after obtaining the opinion of the Advisory Committees of Experts (GPEs). On this basis, EDF carries out safety reassessment studies and defines the modifications to be made. ASN then issues a position statement on the results of these studies and on these modifications, after again consulting the GPEs. This position statement closes the generic phase of the periodic safety review, common to all the reactors. This generic review does not take account of any specific individual aspects and ASN gives a ruling on the suitability of each nuclear power reactor for continued operation, notably on the basis of the results of the conformity checks and the assessment made in the periodic safety review concluding report for the reactor submitted by EDF. Following examination of this report, ASN communicates its analysis to the Ministry responsible for nuclear safety. It can issue new requirements governing its continued operation. A public inquiry is held concerning the concluding report for the periodic safety reviews beyond the 35th year of operation of a nuclear power reactor. Five years after submission of this report, the licensee sends ASN an interim report on the implementation of the requirements stipulated by the review, as a result of which ASN may add to these requirements. 3.3 Ongoing periodic safety reviews in the Nuclear Power Plants 3.3.1 The 900 MWe reactors The fourth periodic safety review EDF’s 32 reactors of 900 MWe in operation were commissioned between 1978 and 1987. More than half of them have reached the milestone of their fourth periodic safety review. This fourth periodic safety review comprises particular challenges: ∙Some items of equipment are reaching their design-basis lifetime. The studies concerning the conformity of the installations and the management of equipment ageing therefore need to be reviewed to take account of the degradation mechanisms actually observed and the maintenance and replacement strategies implemented by EDF. ∙The safety reassessment of these reactors and the resulting improvements must be carried out in the light of the safety objectives of the new-generation reactors, such as the EPR, the design of which meets significantly reinforced safety requirements. The modifications associated with this periodic safety review incorporate those linked to deployment of the “hardened safety core”. ASN’s position statement on the generic phase of the periodic safety review In 2013, EDF sent ASN its proposed objectives for this periodic safety review, notably the level of safety to be achieved for continued operation of the reactors. After examining the objectives proposed by EDF, with the support of IRSN, and following consultation of its GPEs, ASN released a position statement on these objectives and issued additional requests in April 2016. EDF supplemented its programme of work and in 2018 presented ASN with the measures it envisages taking in response to these requests. In 2020, with the support of IRSN, ASN finalised its examination of the generic studies linked to this review. At the beginning of 2021, ASN issued a position statement on the conditions for continued operation of the reactors. ASN considered that the measures planned by EDF combined with those prescribed by itself open up the prospect of continued operation of these reactors for the ten years following their fourth periodic safety review. In October 2023, EDF asked ASN for postponement of the deadlines for some of the requirements in the resolution adopted in February 2021. Unexpected technical issues during implementation of some of the requirements, changes in the refuelling outages schedule, notably linked to the discovery of stress corrosion on the auxiliary lines, unexpected long-duration shutdowns or the needs of the electricity grid during the winter period, as well as a logjam with other periodic safety reviews, creating pressure on its engineering capacity, led EDF to revise its ability to carry out the activities needed to comply with the The ageing of Nuclear Power Plant equipment As in any industrial installation, the equipment in NPPs experiences ageing. This ageing is the result of physical phenomena (corrosion of metals, hardening of polymers, hardening of certain steels under the effect of irradiation or temperature, swelling of certain concretes, etc.) which can degrade their characteristics according to their age or their operating conditions. This degradation obliges the licensee to repair or replace the equipment or to limit the lifetime of non-replaceable equipment, such as the reactor pressure vessel (see point 2.2.4). The ageing management process implemented by EDF is based on three main points: anticipating the effects of ageing as of the design stage, monitoring the actual condition of the facility and repairing or replacing equipment degraded by the effects of ageing. Before being installed, safety-important equipment more particularly undergoes a qualification process to ensure its ability to perform its functions in conditions corresponding to the situations in which it will be needed, accident situations in particular. The management of equipment ageing, and of the risk of obsolescence – which refers to difficulties linked to guaranteeing the procurement of spares over time – are essential to maintaining a satisfactory level of safety. They also contribute to reactor conformity with the applicable rules being maintained over time. The control of ageing is given particular attention by ASN during the fourth periodic safety reviews. The provisions adopted or planned by EDF are examined and inspected, to ensure that the risks associated with ageing and obsolescence are controlled satisfactorily. EDF intends to use a similar approach again for the fifth periodic safety review of the 900 MWe reactors. ASN Report on the state of nuclear safety and radiation protection in France in 2024 319 01 The EDF Nuclear Power Plants 10 02 03 04 05 06 07 08 09 11 12 13 14 15 AP
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