Nuclear generation resources, owing to their low variable cost are first used for base-load generation, immediately after run-of-river hydro-power and other unavoidable renewable energies, as well as the energy purchased under buying obligations from decentralised energy producers. Variations in energy consumption over one year (summer-winter, day-night) and the currently restricted fluidity of wholesale markets due to limited interconnections on the borders lead nuclear energy to be used also for mid-merit generation. High variations in seasonal consumption in France and its major variation during winter months require that planned nuclear fleet outages be concentrated between April and October.
The nuclear fleet produced 360.7TWh in 2021, up 25.3TWh compared to that of 2020. The increase in generation in 2021 compared with 2020 was due in particular to:
In addition, the Covid health crisis resulted in a greater number of planned outages in 2021 following the postponements decided in 2020.
The main developments that impacted generation in 2021 were:
With respect to unit shutdowns, performance remains below target. Several reactors experienced overruns exceeding 60 days including Cruas 1 (VP), Civaux 2(VP), Grave lines 4 (VP), St Laurent B1 (VP), Golfech 2 (VP) and Cattenom 2 (ASR). However, the performance of Tricast in, which carried out the partial inspection of reactor 1 25 days ahead of the initial schedule, is noteworthy.
The Start 2025 transformation programme is a multi-year plan that aims to improve the industrial control of unit outages and their long-term performance.
Nuclear generation expressed in annual energy corresponds to a load factor rate referred to as “Kp” for the French nuclear fleet (defined as the ratio of energy generated to the maximum theoretical energy, or the energy generated if the installed capacity were operated year-round). This rate is obtained by multiplying two coefficients (Kp = Kd × Ku):
In 2021, the Kp factor reached 67%, an increase compared with that of 2020 (61.6%). This results from a Kd of 72.9%, higher than in 2020 (71.9%) and a Ku of 92.2%, also higher than in 2020 (85.7%).
Following the discovery of evidence of stress corrosion in the SIS circuits of Civaux 1during its ten-year inspection, it was decided to shut down the Civaux 2 (November 2021), Chooz 1 (December 2021) and Chooz 2 (December 2021) reactors (3). The inspections carried out on these reactors revealed similar evidence. During the ten-year inspection of Penly reactor 1 (1,300 series), preventive maintenance checks revealed similar evidence in the SIS circuit (4).
After analysing the results of the non-destructive examinations carried out during the last ten-yearly outage programmes for the 56 reactors in the nuclear fleet and the results of the latest laboratory assessments, EDF has drawn up a prioritised list of reactors on which inspections will be carried out:
In addition, EDF is continuing to define a plan for inspections across the nuclear fleet, with the aim of carrying them out by the end of 2022, during scheduled maintenance and fuel renewal outages of several 1,300MW and 900 MW reactors. EDF is continuing its studies to complete its knowledge of the phenomenon and has initiated the development of new ultrasonic inspection means capable of measuring the cracks depth. EDF plans to inspect its reactors with these new methods from September 2022 until the end of 2023.
Technical exchanges continue with the Nuclear Safety Authority, which is regularly informed of the results of inspections and expert reports.
At the date of filing of this document, the Group is awaiting the position from the investigation carried out by the French Nuclear Safety Authority on the evidence of stress corrosion and the corrective measures considered.
The programme for inspecting and repairing the pipes that are potentially concerned by the phenomenon of stress corrosion constitutes a major risk in terms of nuclear generation. In response, the Group has reviewed its estimate of nuclear generation for 2022 and 2023(5). To date, the Group is not in a position to analyse the impacts beyond 2023.
This risk that the Group is facing is described in section 2.2.5 “Specific risks relating to nuclear activities” – Risk 5A “Failure to meet operating and/or continued operating targets for nuclear fleets (France and United Kingdom)”.
The risks related to the environment, nuclear safety and radiation protection are described in Chapter 2 under risk 5C “Nuclear safety violations during operations resulting in nuclear civil liability”.
EDF’s environmental procedure was introduced in 2002 on a few sites, then extended to all nuclear generation units. It is based on an ISO 14001-certified SME environmental management system (see section 3.5.4.2 “The environmental management system (EMS)”).
For a description of radioactive waste processing downstream of the fuel cycle as well as decommissioning, see sections 1.4.1.1.2.3 “The issues relating to the nuclear activity”, “The nuclear fuel cycle and related issues” and “Decommissioning of nuclear power plants”.
(1) The safety injection system (SIS) is a backup system that cools the reactor in the event of an accident.
(2) Available energy is equal to the maximum theoretical energy less generation losses due to technical reasons inherent to power plants, such as planned outages, unplanned outages due to failure or safety requirements, and performance of regulatory tests.
(3) See the EDF press release of 15 December 2021 “Reactors of Civaux and Chooz nuclear power plants: replacements and preventive checks on parts of the piping of a safety system”.
(4) See the EDF press release of 13 January 2022 “EDF updates its nuclear output estimate in France for 2022”.
(5) See EDF press release of 7 and 11 February 2022.
