LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT In the light of the potential risks from the failure of this equipment, both for reactor safety and the safety of the personnel, there are regulations that govern their design, manufacture and operation, designed to preclude their failure. These requirements for example concern the strength of the materials used, the design calculations to be performed, or the ability to inspect the equipment during operation. Under the regulations, the manufacturer of an NPE is responsible for ensuring that its design and manufacture comply with these requirements, taking into account the specific requirements arising from the reactor safety case. Subsequently, EDF, as the reactor licensee, is responsible for installing and operating the NPE. 2.2.2 – Assessment of the design and manufacturing of Nuclear Pressure Equipment ASNR assesses the compliance with the essential safety requirements imposed by the regulations, of the NPE most important for safety, referred to as “level N1”, corresponding primarily to the reactor pressure vessel, the SGs, the pressuriser, the reactor coolant pump sets, the piping, notably that of the Main Primary and Secondary (MPS and MSS) Systems, as well as the safety valves. ASNR can be assisted in this task by organisations that it approves and oversees. The conformity assessment of the other NPE (“level N2 or N3”) is carried out directly by these approved organisations. Four inspection organisations or bodies are currently approved by ASNR to assess NPE compliance: Apave Exploitation France, Bureau Veritas Exploitation, Vinçotte International and the inspection body of the EDF users. This conformity assessment concerns the equipment intended for the new nuclear facilities (more than 200 equipment items for the Flamanville EPR reactor) and the spare equipment intended for nuclear facilities already in service (notably the replacement steam generators). It takes the form of an examination of the technical documentation of each equipment item and inspections in the workshops of the manufacturers, as well as at their suppliers and subcontractors. In 2025, ASNR continued to assess the supply of large forgings for the equipment destined for the EPR 2 reactors (vessels, steam generators, reactor coolant pump sets) and began to monitor production at Framatome plants. ASNR also inspected suppliers and manufacturers of NPE at levels N2 and N3, focusing in particular on certain sensitive sectors such as foundries and pipe manufacturers. The NPE manufacturing operations involve a large number of suppliers, to which the manufacturers sometimes subcontract activities that are decisive for the mechanical strength of the equipment produced. In this context, ASNR reinforced its checks, following the deficiencies it had identified at certain materials suppliers concern the control of sensitive manufacturing processes (such as welding or casting), or the traceability of manufacturing operations. 2.2.3 – Operation of Nuclear Pressure Equipment The reactor MPS and MSS, which contribute to the containment of the radioactive substances, to cooling and to controlling reactivity, operate at high temperature and high pressure. The monitoring of the operation of these systems is regulated by the Order of 10 November 1999 relative to the monitoring of operation of the MPS and the MSS of PWRs. These systems are thus the subject of monitoring and periodic maintenance by EDF. These systems are in particular subject to periodic requalification every ten years, which comprises a complete inspection of the systems involving non-destructive examinations of the most 1. Tearing of a material under the effect of stresses applied to it, following deformation. sensitive areas, hydrostatic pressure testing and verification of the good condition and good operation of the over-pressure protection accessories. The licensee is also required to keep and update files on the design, manufacture, overpressure protection, materials, findings made during operation and, as applicable, processing of deviations, as often as necessary and at the time of the periodic requalifications. Some of the safety issues of the components of the primary or secondary systems are detailed below. The reactor pressure vessels The reactor pressure vessel is an essential component of a PWR and contains the reactor core and a part of its instrumentation. In normal operating conditions, the vessel is entirely filled with water, at a pressure of 155 bar and a temperature of approximately 300°C. It is made of ferritic steel, with a stainless steel inner liner. Regular inspection of the condition of the vessel is essential for several reasons: ∙The consequences of rupture of this equipment are not studied in the reactor safety case. Monitoring thus contributes to the break preclusion approach adopted for this equipment. This approach is based on particularly stringent design, manufacturing and in-service inspection provisions in order to guarantee its strength throughout the life of the reactor, including in the event of an accident. ∙During operation, the vessel’s metal slowly becomes brittle, under the effect of the neutrons from the fission reactions in the core. This embrittlement more particularly makes the vessel more susceptible to thermal shocks under pressure, or to sudden pressure rises when cold. This susceptibility is also aggravated by the presence of technological flaws, which is the case for some vessels with manufacturing defects under their stainless steel liner. ∙The vessel is a component for which replacement is not envisaged, owing to both technical feasibility and cost. Cast components of the main primary system The MPS of some of the reactors of the French fleet comprises several austenitic-ferritic stainless steel cast elbow and nozzle assemblies. The ferritic phase of this steel experiences ageing under the effect of temperature. Certain alloy elements present in the material, molybdenum in particular, aggravate this ageing sensitivity, notably on the 900 MWe reactors and the first 1,300 MWe reactors. The result is a deterioration of certain mechanical properties, such as toughness and resistance to ductile tearing(1). The elbows also comprise flaws inherent in the static casting manufacturing method. The effects of thermal ageing lessen the fast fracture resistance margins in the presence of defects. EDF has carried out extensive work to learn more about these materials, their ageing kinetics and to assess the fast fracture margins. These elbows are attentively monitored by ASNR, insofar as the continued operation of these components of the main primary system must be justified on the occasion of each periodic safety review, while taking account of this ageing phenomenon. There are particular issues with regard to some cast elbows on the 900 and 1,300 MWe reactors, which are directly connected to the reactor vessel, because they are very hard to replace. The steam generators The SGs comprise two parts, one of which is a part of the MPS and the other a part of the MSS. The integrity of the main components of the SGs is monitored, more specifically the tubes making up the tube bundle. This is because any damage to the tube bundle (corrosion, wear, cracking, etc.) can lead to a primary system leak to the secondary system. In addition, rupture of one of the tubes in the bundle would lead to bypassing of the reactor containment, which is the third containment barrier. The SGs are the subject of a ASNR Report on the state of nuclear safety and radiation protection in France in 2025 287 01 05 02 06 03 07 04 08 09 10 11 13 12 A / Z
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