2.4 Risk prevention and management 2.4.1 The General Operating Rules The 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 (STE), 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 amend them temporarily on an ad hoc basis, 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 longterm 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. More broadly, it ensures that the measures planned and taken by EDF for operation of the reactors, are appropriate to the risks created by this operation. Normal operation During its NPP inspections, ASN notably verifies that the licensee complies with the STEs and, if applicable, the compensatory measures associated with any temporary modifications. It also checks the consistency between the modifications made to the facilities and those made to the documents used by the reactor control teams, such as operational control instructions and alarm sheets. It also ensures that the procedures used to configure the systems or lock out equipment do actually take account of the requirements arising from the STEs. Finally, it is attentive to the good understanding and good application of these various documents by the control teams and the correct management of sensitive activities, which are often the cause of anomalies. Failures to comply with the STE constitute significant events which are to be reported to ASN. ASN analyses the origin and consequences of these events and, during its inspections, checks that measures have been taken by the licensee to correct the deviations and prevent them from happening again. The situations in which the reactors were operated outside the specified limits were fewer in number in 2022 than in 2021. The steps taken by EDF on this subject would appear to paying off. However, ASN finds that the quality of surveillance in the control room deteriorated in 2022. This situation sometimes led to belated identification of equipment unavailability, which could lead to non-compliance with the STEs. In addition, the number of significant events linked to system configuration faults reached a noticeably higher level than in 2021. Most of the sites are concerned by this increase. These faults can be caused by failure to comply with procedures or by incomplete procedures. In 2023, ASN will reinforce its inspections on these topics. ASN checks that the periodic tests of safety important equipment items do effectively check their operation and level of performance. It carries out this verification when RGE modification authorisation applications are submitted. During inspections, it also verifies that these periodic tests are carried out in accordance with the test programmes stipulated in the RGEs. ASN Report on the state of nuclear safety and radiation protection in France in 2022 295 • 10 • The EDF Nuclear Power Plants 10 01 07 08 13 AP 04 06 12 14 03 09 05 11 02
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