ASN Report 2018

2.4  ̶  Risk prevention and control 2.4.1  –  Monitoring the drafting and application of the general operating rules The General Operating Rules (RGE) cover the operation of nuclear power 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. • Normal and degraded operations Operating Technical Specifications The Operating Technical Specifications (STE), which constitute Chapter III of the General Operating Rules, define the normal operating conditions based on the design and sizing hypotheses of the facility and require the systems necessary for maintaining 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 what is to be done if a required system momentarily fails or if a limit is exceeded, situations which constitute “degraded operation”. The STE evolve to take account of the lessons learned from their application and the modifications made to the reactors. On an occasional basis, the licensee can also modify them temporarily, for example to carry out an intervention in conditions that are different from those initially considered in the nuclear safety case. It must then demonstrate the pertinence of this temporary modification and define adequate compensatory measures in order to control the corresponding risks. Depending on their importance, STE modifications likely to affect protected interests require either an authorisation application sent to ASN, or notification to ASN before they are implemented. During inspections in NPPs, ASN verifies that the licensee complies with the STE and, as necessary, checks the compensatory measures associated with any temporary modifications. It also checks the consistency between the modifications made to the facilities and the normal operating documents, such as instructions, alarm sheets, the STE and the training of the persons responsible for implementing them. Periodic tests Elements Important for the Protection (EIP) of persons and the environment are equipment items identified by the licensee. They undergo qualification to guarantee their ability to perform their assigned functions in the situations in which they are needed. The periodic tests of this equipment help verify that this qualification is maintained and regularly ensure that these elements are available when required. The corresponding rules, incorporated into the reactor general operating rules, set the nature of the technical checks to be performed, their frequency and the criteria for determining the satisfactory nature of these checks, in other words the compliance of the equipment concerned with the qualification requirements. ASN ensures that the periodic tests on the EIP are relevant and are continuously improved. It carries out this verification when examining the application for authorisation to start-up the reactor and then the applications for authorisation to modify the RGE. In addition, during inspections, it verifies that these periodic tests are carried out in accordance with the test programmes stipulated in the RGE. Core physics tests The core physics tests contribute to the first two levels of defence in depth. Their purpose 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 RGE chapter concerning EDF reactor core physics tests, are performed periodically. The physics tests at restart are comparable to requalification tests following reloading of the core. The physics tests during the cycle and for the cycle extension guarantee the availability and representativeness of the instrumentation as well as the performance of the core in operation. The modifications to the RGE concerning core physics tests are made using a process similar to that for STE modifications and generally require ASN authorisation. During the on-site inspections, ASN checks the conformity of the tests performed (compliance with procedures and criteria to be verified) and EDF’s organisation during these particular operating phases. • Operating rules in the event of an incident or accident Incident or accident operations The strategies and reactor operating rules for an incident or accident situation are defined in the RGE. These evolve more particularly 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. Most of these modifications require ASN authorisation. ASN regularly checks the processes to draft and validate the incident or accident operating rules, their pertinence and how they are implemented. To do this, ASN can place the facility’s control teams in a simulated situation to check how they apply the above- mentioned rules and manage the specific equipment used in accident operating situations. It in particular ensures correct application of the emergency teams’ organisation principles described in the EDF baseline requirements validated by ASN. This organisation more particularly requires that each emergency team member take part in at least one exercise per year. 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 following severe fuel damage. When faced with such unlikely situations, the installation control strategies place emphasis on preserving the containment in order to minimise releases into the environment as much as possible (see chapter 4, point 1.3.1). The implementation of these strategies requires the participation of the local and national emergency teams. These teams use the On-site Emergency Plan (PUI) plus the severe accident operation guide and the emergency team action guides in particular. ASN periodically examines the strategies presented by EDF in these documents, in particular for the reactor periodic safety reviews. ASN report on the state of nuclear safety and radiation protection in France in 2018  285 10 – EDF NUCLEAR POWER PLANTS 10