Other equipment takes part in the containment function, such as the systems for accessing the interior of the containment (airlocks and equipment hatch), the circuit depressurising the annulus between the double-wall containments, and the control room ventilation system. 2.3.2 Assessment of the containments Overall management of the containment function EDF’s management of the containment function is on the whole satisfactory. ASN however still observes occasional but recurring unavailabilities affecting certain equipment participating in the containment function. These unavailabilities notably concern the containment penetrations pressurisation system and leak monitoring system, as well as the control room ventilation system. Since 2014, EDF has been carrying out an action plan with the aim of guaranteeing that the flowrates in the ventilation systems meet the safety requirements both for the containment and for thermal conditioning of the installations, in the light of the changes made to the reactors since they were built. The action plan is being deployed, reactor by reactor, on all the ventilation systems concerned, and includes an inventory of the equipment and ducts. As necessary, EDF carries out repairs and improvements and adjusts the ventilation flow rates. The final phase of this national action plan includes a programme to ensure the lasting nature of the adjustments made. ASNR will issue a position statement on this subject in 2025. Single-wall containments with an internal metal sealing liner The ten-yearly tests on the 900 MWe reactor containments carried out since 2019 as part of their fourth ten-yearly outages did not bring to light any generic problems liable to compromise their operation. In 2024, five single-wall containment reactors carried out their containment building pressure tests and the results were satisfactory. Double-wall containments The tests on the double-wall containments performed during the first tenyearly outages of the 1,300 MWe reactors detected a rise in the leak rate from the inner wall of some of them, under the combined effect of concrete deformation and a loss of pre-stressing of certain tendons, that was greater than anticipated at the design stage. EDF then initiated major work consisting in locally applying a resin sealing coating to the interior and exterior surfaces of the inner wall of the containments of the most severely affected 1,300 MWe reactors, as well as to the 1,450 MWe reactors. For all the reactors on which it was carried out, this work enabled the leak rate criteria to be met during the containment pressure tests. In 2024, a double-wall reactor underwent its building pressure test, the result of which was satisfactory. ASN remains particularly attentive to changes in the double-wall containment leak rates and to the steps taken by EDF to control them. 2.4 Organisation for reactor operations 2.4.1 Reactor operations The Order of 7 February 2012 stipulates that the licensee must have the technical skills needed to manage the activities involved in operation. Furthermore, this Order requires that the licensee define and implement an Integrated Management System (IMS) to ensure that the requirements concerning nuclear safety and protection of the environment are systematically considered in any decision concerning the facility. This IMS must specify the steps taken with regard to organisation and to resources of all kinds, in particular those adopted to control the activities important for the protection of persons and the environment. Normal operation The EDF NPPs are permanently monitored from a control room by a control team which is also in charge of controlling the installations. The operating limits within which the teams must keep the installation are defined in the RGEs. The licensee ensures that this is done using normal operating documentation, in particular the operating instructions and alarm data sheets. The licensee is regularly required to modify the installation’s configuration to allow intervention by the maintenance crews, to test the availability of a system or to change the status of the reactor. Tests are regularly performed to check the correct working of the systems which could be required in an incident or accident situation and to check the correct behaviour of the reactor’s core. Some tests are performed with the reactor operating, while others can only be carried out during reactor outages. The control teams perform some of these tests themselves, while others require intervention by specialised teams. General Operating Rules The RGEs present the provisions the licensee intends to implement to operate its installation in compliance with the safety case. They notably specify the rules to be followed in normal operation, the periodic tests to be carried out and the control operations required in an incident or accident situation. They are one of the items making up the commissioning authorisation application for a nuclear reactor. The operating technical specifications included in the RGEs define the parameters required in normal operation. They also identify the systems essential to maintaining the safety functions and specify what to do in the event of momentary unavailability of a required system or if a limit is exceeded. With regard to periodic tests, the RGEs detail the checks to be carried out, their frequency, and the criteria for acceptance of the results. There are in particular tests to check that the reactor core complies with the design baseline safety requirements and the safety case and to calibrate the automatic control and protection systems. The incident or accident situation control procedures, which are included in the RGEs, detail the steps to be taken by the control teams in these situations in order to restore normal operation or, in the event of an accident, to return the installation to a safe state and limit its consequences. EDF regularly updates these documents in order to incorporate OEF and take account of the modifications made to the reactors. Temporary amendments can also be made. They require justification and the definition of compensatory measures to control any associated risks. Depending on their significance, RGEs noteworthy modifications that could affect the safety of the installation or protection of the environment, require either submission of an authorisation application to ASN or notification to ASN before they are implemented. ASN Report on the state of nuclear safety and radiation protection in France in 2024 305 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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