regularly finds points for improvement, such as addressing various hazards or preparing for activities. The procurement of non-conforming spare parts once again in 2021 led to faults in the management of the activities. Incorrectly applied national EDF documents or incorrect operational documents are also the cause of inappropriate maintenance operations or maintenance quality defects. Finally, ASN observed that the requalification tests are not always able to detect equipment defects following maintenance or modification work. Despite an improvement observed in 2019 and 2020 in the technical oversight of the work and contractor monitoring, particularly through the use of computer tools recently deployed in the NPPs, there were still numerous significant events arising from maintenance non-quality, undetected by monitoring or by the first level analyses. In the context of the continued operation of the reactors, the “major overhaul” programme and all the modifications made as a result of the lessons learned from the accident at the Fukushima Daiichi NPP, ASN considers that it is important for EDF to continue with its efforts to remedy the difficulties encountered and improve the quality of its maintenance activities. In 2021, through its inspections, ASN found that the various sites did on the whole deploy the maintenance policy changes initiated by EDF as of 2016. 2.4.5 Protection against internal and external hazards Fire risks A fire can lead to failure of the equipment needed to control the fundamental safety functions. Steps must thus be taken to protect the sensitive parts of the facility against fire. In the same way as the other BNIs, NPPs are covered by ASN resolution 2014-DC-0417 of 28 January 2014, relating to the rules applicable to BNIs for controlling fire risks. The way the fire risk is taken into account in the NPPs is based on the principle of “Defence-in-Depth” built around three levels, that is the design of the facilities, fire prevention and firefighting. Design rules aim to prevent a fire from spreading and mitigate its consequences; they are based primarily on “fire sectorisation”. This involves dividing the facility into sectors and containment areas designed to keep the fire within a given perimeter bounded by items (doors, walls and fire dampers) offering a specified fire resistance duration. The main purpose is to prevent a fire spreading to two redundant equipment items performing a fundamental safety function. Prevention primarily consists in: ∙ ensuring that the nature and quantity of combustible material in the premises remains below the hypotheses adopted for fire sectorisation; ∙ identifying and analysing the fire risks, in order to take steps such as to avoid them. More specifically, for all the work liable to generate a fire, a “fire permit” must be issued and protective measures taken. Finally, the detection of an outbreak of fire and fire-fighting measures should enable a fire to be brought under control and then extinguished within a time compatible with the fire resistance duration of the sectorisation elements. Explosion risks An explosion can damage the items essential for maintaining safety or lead to rupture of the containment and the dispersal of radioactive materials into the facility, or even into the environment. Steps must thus be taken by the licensee to protect the sensitive parts of the facility against explosions. REACTOR OUTAGES The nuclear power reactors must be periodically shut down for replacement of the fuel depleted during the electricity production cycle. One third or one quarter of the fuel is thus renewed at each outage. These outages means that certain parts of the installations which are not accessible during the production phase then become temporarily accessible. They are thus put to good use by EDF to carry out checks, tests and maintenance, as well as to perform works on the facility. These refuelling outages can be of several types: ཛྷ Refuelling Outage and Maintenance Outage: these outages, which last a few weeks, are devoted to replacing a part of the fuel and to carrying out a verification and maintenance programme, which is more extensive during a maintenance outage than during a refuelling outage. ཛྷ Ten-yearly outage: this is an outage involving a programme of in-depth verification and maintenance. This type of outage, which lasts several months and takes place every ten years, enables the licensee to carry out large-scale operations such as the complete inspection and hydraulic testing of the reactor coolant system, hydrotesting of the containment or incorporation of design changes resulting from the periodic safety reviews. These outages are scheduled and prepared by the licensee several months in advance. ASN checks the steps taken by the licensee to ensure the safety of the facility, environmental protection and radiation protection of the workers during the outage, as well as the safety of the reactor for the next production cycle. In the light of the provisions of its resolution 2014-DC0444 of 15 July 2014 concerning shutdowns and restarts of pressurised water reactors, the monitoring performed by ASN primarily concerns: ཛྷ during the outage preparation phase, the content of the outage programme drawn up by the licensee. As necessary, ASN may ask for additions to this programme; ཛྷ during the outage, through regular briefings and inspections, the implementation of the programme and the handling of any unforeseen circumstances; ཛྷ at the end of the outage, on the condition of the reactor and its suitability for restart. It is after this inspection that ASN will either approve reactor restart, or not; ཛྷ after reactor restart, the results of all the tests performed during the outage and in the restart phase. Since 2020, ASN has reduced the volume of its documentary examinations for reactor outages and has increased its field inspections. These new oversight methods enable ASN’s resources to be targeted on the activities with the highest risks and this oversight to be made more efficient. ASN Report on the state of nuclear safety and radiation protection in France in 2021 291 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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