In 2021, ASN ran a dedicated inspection campaign on the action plan for the ventilation systems. ASN found that it is correctly implemented on the reactors and that the corresponding safety requirements are met. In 2022, EDF will run a programme to ensure the sustainability of the settings needed for correct operation of the ventilation systems determined by this action plan. ASN will examine the pertinence of this programme. Single wall containments with an internal metal sealing liner The ten-yearly tests on the 900 MWe reactor containments carried out since 2009 as part of their third ten-yearly outages did not bring to light any generic problems liable to compromise their operation. The containment of Bugey NPP reactor 5 did however need to be repaired, following damage to the tightness of its metal liner at the lower part of the reactor building, observed in 2015. EDF subsequently implemented specific monitoring of this containment. The tightness of this containment also received particular attention during the fourth ten-yearly outage of this reactor in 2021. The results of the pressure test on this containment performed in 2021 were satisfactory. The results of the pressure tests performed as part of the fourth ten-yearly outages has so far also proven to be satisfactory. Double-wall containments The tests on the double-wall containments performed during the first ten-yearly outages of the 1,300MWe 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 prestressing 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 1,300MWe reactors, as well as to the 1,450MWe 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. ASN remains vigilant with regard to changes in the leaktightness of these containments and to maintaining the long-term effec– tiveness of the coatings. 2.4 Risk prevention and management 2.4.1 The General Operating Rules The General Operating Rules (RGEs) cover the operation of nuclear power generating reactors. These are drafted by the licensee and are the operational implementation of the hypotheses and conclusions of the safety assessments constituting the nuclear safety case. They set the limits and conditions for operation of the installation. Depending on their significance, RGE modifications that could affect safety require either submission of an authorisation application to ASN or notification to ASN before they are implemented. Normal operation Operating Technical Specifications The Operating Technical Specifications (STEs), which are part of the RGEs, define the normal operating conditions based on the facility’s design and sizing hypotheses and identify the systems needed to maintain the safety functions, in particular the integrity of the radioactive substances containment barriers and the monitoring of these functions in the event of an incident or accident. They also stipulate the action to be taken in the event of temporary failure of a required system or if a limit is exceeded, situations which constitute “degraded mode” operation. EDF regularly updates the STEs to incorporate the lessons learned from their application and the modifications made to the reactors. The licensee can also modify them temporarily if need be, for example to carry out an operation in conditions that differ from those initially considered in the nuclear safety case. The licensee must then demonstrate the relevance of this temporary modification and define adequate compensatory measures to control the associated risks. Periodic tests The Protection Important Component (PIC) of persons and the environment undergo qualification to guarantee their ability to perform their assigned functions in the situations where they are needed. They must be tested in order to verify the long-term validity of their qualification. The periodic test rules for equipment important for safety are incorporated into the RGEs. They set the nature of the technical checks to be performed, their frequency and the criteria for determining the satisfactory nature of these checks. Core physics tests The purpose of core physics tests is, on the one hand, to confirm that the core in operation is compliant with the design baseline requirements and the safety case and, on the other, to calibrate the automatic control and protection systems. These tests, prescribed in the RGEs, are performed periodically. The physics tests at restart are comparable to requalification tests following reloading of the core. The physics tests during a cycle and a cycle extension guarantee the availability and representativeness of the instrumentation as well as the characteristics of the core in operation. Operating rules in the event of an incident or accident Operation in the event of an incident or accident The RGEs also deal with the reactor operating procedures in an incident or accident situation. They specify the operations to be performed by the shift crew when the reactor experiences an incident or accident situation; these operations aim to restore the reactor to normal operation or, for accident situations, to mitigate the consequences. The control teams are regularly trained in the use of these procedures. EDF is updating these procedures to take account of experience feedback from incidents and accidents, to correct the anomalies detected during their application or to take account of modifications made to the facilities, in particular those resulting from the periodic safety reviews. Operation in a severe accident situation Following an incident or accident, if the safety functions (control of reactivity, cooling and containment) are not guaranteed owing to a series of failures, the situation is liable to develop into a severe accident with severe fuel damage. When faced with such unlikely situations, the installation control strategies place emphasis on preserving the integrity of the containment in order to minimise releases into the environment. The implementation of these strategies mobilises the expertise of the local and national emergency teams. These teams draw on the On-site Emergency Plan (PUI) plus the severe accident intervention guide and the emergency teams action guides in particular. 2.4.2 Assessment of reactor operations ASN checks the content of the RGEs during their examination prior to implementation, and monitors application of the RGEs during inspections. Normal operation During NPP inspections, ASN verifies that the licensee complies with the STEs and, if applicable, the compensatory measures associated with any temporary modifications. It also checks the ASN Report on the state of nuclear safety and radiation protection in France in 2021 289 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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